Delisle to Celsius Converter
Convert degrees Delisle to degrees Celsius with our free online temperature converter.
Quick Answer
1 Delisle = 99.333333 degrees Celsius
Formula: Delisle × conversion factor = Celsius
Use the calculator below for instant, accurate conversions.
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All conversion formulas on UnitsConverter.io have been verified against NIST (National Institute of Standards and Technology) guidelines and international SI standards. Our calculations are accurate to 10 decimal places for standard conversions and use arbitrary precision arithmetic for astronomical units.
Delisle to Celsius Calculator
How to Use the Delisle to Celsius Calculator:
- Enter the value you want to convert in the 'From' field (Delisle).
- The converted value in Celsius will appear automatically in the 'To' field.
- Use the dropdown menus to select different units within the Temperature category.
- Click the swap button (⇌) to reverse the conversion direction.
How to Convert Delisle to Celsius: Step-by-Step Guide
Temperature conversions like Delisle to Celsius use specific non-linear formulas.
Formula:
°C = 100 - °De × 2/3Example Calculation:
Convert 10°De: 100 - (10 × 2/3) = 93.3°C
Disclaimer: For Reference Only
These conversion results are provided for informational purposes only. While we strive for accuracy, we make no guarantees regarding the precision of these results, especially for conversions involving extremely large or small numbers which may be subject to the inherent limitations of standard computer floating-point arithmetic.
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View all Temperature conversions →What is a Delisle and a Celsius?
The Delisle scale (symbol: °De or °D) is an inverted temperature scale that divides the interval between the boiling point and freezing point of water into 150 equal divisions under standard atmospheric pressure, with numerical values decreasing as temperature increases.
Scale Calibration (Inverted)
Fixed Points:
- Boiling point of water: 0 degrees Delisle (0°De) - the ZERO reference
- Freezing point of water: 150 degrees Delisle (150°De) - 150° higher than boiling
- Degree size: Each Delisle degree = 2/3 Celsius degree (or 0.667°C)
The Inversion: Unlike Celsius, Fahrenheit, Réaumur, and Kelvin, which all increase with temperature:
- Hotter temperatures = LOWER Delisle numbers (approaching 0°De)
- Colder temperatures = HIGHER Delisle numbers (above 150°De)
- Temperature increases = Delisle decreases
Mathematical Relationships
Delisle to Celsius:
- °C = 100 - (°De × 2/3)
- Or: °C = 100 - (°De ÷ 1.5)
Celsius to Delisle:
- °De = (100 - °C) × 3/2
- Or: °De = (100 - °C) × 1.5
Delisle to Fahrenheit:
- °F = 212 - (°De × 6/5)
- Or: °F = 212 - (°De × 1.2)
Examples:
- 0°De = 100°C (boiling water)
- 75°De = 50°C (halfway between boiling and freezing)
- 150°De = 0°C (freezing water)
- 300°De = -100°C (extreme cold, -148°F)
Why 150 Degrees?
Delisle chose 150 degrees for the freezing point due to:
- Mercury contraction observation: His mercury thermometers showed 150 units of contraction between boiling and freezing
- Divisibility: 150 = 2 × 3 × 5², offering factors (2, 3, 5, 6, 10, 15, 25, 30, 50, 75, 150)
- Convenient fractional divisions: 150/3 = 50°, 150/2 = 75°, 150/10 = 15° for practical measurements
- Empirical basis: Based on actual instrument behavior rather than abstract decimal preference
Why Invert the Scale?
Delisle's inversion was methodological rather than arbitrary:
Calibration Process:
- Started with boiling water (100°C) as reference point zero
- Observed mercury column contraction as water cooled
- Counted degrees of contraction downward from boiling
- At freezing point (0°C), mercury had contracted 150 divisions
Result: A scale that measured "degrees of cooling" from boiling, making hotter temperatures numerically smaller. While counterintuitive by modern standards, it reflected the experimental process.
What Is Celsius?
Degree Celsius (°C) is a unit of temperature on the Celsius scale, a temperature scale originally named "Centigrade" and renamed to honor Swedish astronomer Anders Celsius. It is the most common temperature scale used worldwide, adopted by virtually every country for everyday measurements and scientific work.
The Celsius scale is defined by two fixed points:
- 0°C: The freezing point of water at standard atmospheric pressure (1 atmosphere)
- 100°C: The boiling point of water at standard atmospheric pressure
The scale is divided into 100 equal intervals between these two points, making it a decimal-based (base-10) system that aligns perfectly with the metric system.
Modern scientific definition: Since 1954, Celsius has been defined relative to the Kelvin scale (the SI base unit for temperature):
- °C = K − 273.15
- K = °C + 273.15
This means a change of 1°C equals exactly a change of 1 K, but the zero points differ by 273.15 degrees.
Celsius vs. Other Temperature Scales
Celsius vs. Fahrenheit:
- Celsius: 0°C freezing, 100°C boiling (100-degree range)
- Fahrenheit: 32°F freezing, 212°F boiling (180-degree range)
- Conversion: °F = (°C × 9/5) + 32
- Use: Celsius used globally except US; Fahrenheit used primarily in US
Celsius vs. Kelvin:
- Celsius: Relative scale, can be negative, 0°C = freezing
- Kelvin: Absolute scale, no negative values, 0 K = absolute zero (-273.15°C)
- Conversion: K = °C + 273.15
- Use: Kelvin used in scientific contexts; Celsius for practical applications
Why Celsius is intuitive: The reference points (0°C and 100°C) are based on water phase transitions, which are fundamental to everyday life:
- Below 0°C: Water is solid (ice)
- 0°C to 100°C: Water is liquid
- Above 100°C: Water is gas (steam)
This makes Celsius immediately relatable—anyone who has seen ice melt or water boil understands these reference points.
Note: The Delisle is part of the imperial/US customary system, primarily used in the US, UK, and Canada for everyday measurements. The Celsius belongs to the metric (SI) system.
History of the Delisle and Celsius
The Delisle scale's 290-year history is inseparable from the development of Russian science and the Imperial Academy's early years.
Joseph-Nicolas Delisle (1688-1768)
Born in Paris to artistic parents, Delisle became one of France's leading astronomers, specializing in celestial mechanics and cartography. His work on planetary transits and lunar theory earned him election to the French Academy of Sciences (1714) and international recognition.
1725: Invitation to Russia
Tsar Peter the Great, determined to modernize Russia through Western science, invited Delisle to St. Petersburg to establish an astronomical observatory and help found the Imperial Russian Academy of Sciences. Delisle arrived in St. Petersburg in August 1725, months after Peter's death, but Empress Catherine I honored the invitation.
1725-1747: Russian Academy Directorship
As the Academy's first director of astronomy, Delisle:
- Established St. Petersburg Observatory (1726)
- Trained Russian astronomers and instrument makers
- Standardized scientific measurements across the Russian Empire
- Corresponded with European scientific societies
Creation of the Delisle Scale (1732)
The Problem: Russia's vast territory and extreme climate variations required standardized temperature measurements for meteorology, agriculture, and scientific research. Existing thermometers used inconsistent scales, making comparison impossible.
Delisle's Solution (1732):
- Boiling water reference: Started with boiling point as 0° (easiest to reproduce reliably)
- Mercury contraction: Observed mercury column shrinking as temperature decreased
- Freezing point calibration: Marked freezing water at 150° of contraction
- Uniform divisions: Divided the interval into 150 equal degrees
1732 Paper: Delisle presented his scale to the Imperial Russian Academy, arguing that starting from boiling point provided greater calibration accuracy than starting from freezing (where ice-water mixtures could vary slightly).
Official Adoption in Russia (1738-1840s)
1738: Imperial Decree
The Russian Imperial government officially adopted the Delisle scale for all government and scientific purposes, making Russia the first nation to standardize on a single temperature scale nationwide.
Implementation:
- Meteorological stations: All Russian weather observation posts used Delisle thermometers
- Scientific research: Academy publications reported temperatures in Delisle
- Military applications: Army and Navy used Delisle for weather reporting
- Educational institutions: Russian universities taught Delisle as standard
Geographic Spread: The scale's use extended across the Russian Empire:
- St. Petersburg and Moscow (primary centers)
- Baltic provinces (Estonia, Latvia, Lithuania)
- Siberian outposts and exploration expeditions
- Crimea and southern territories
Coexistence with Réaumur (1780s-1840s)
By the late 18th century, Western European science had largely standardized on Réaumur (continental Europe) or Fahrenheit (Britain), creating communication challenges for Russian scientists.
1780s-1820s: Gradual Transition
Russian instrument makers began producing dual-scale thermometers (Delisle/Réaumur) to facilitate:
- International scientific correspondence
- Translation of Western European research
- Trade with European partners
1840s: Réaumur Dominance
By the 1840s, Réaumur had effectively replaced Delisle in Russian scientific practice:
- Younger Russian scientists trained with Réaumur
- International standardization pressure increased
- French scientific influence (Réaumur) outweighed earlier German connections
Final Decline (1850-1917)
1850-1870: Delisle relegated to historical archives, antique thermometers, and elderly scientists' habit 1871: German unification's adoption of Celsius influenced Russian scientific circles 1900-1917: Celsius gaining ground in Russian universities and research institutions 1917-1925: Bolshevik Revolution brought metric system adoption, officially ending Delisle use
Legacy and Modern Recognition
The Delisle scale survives as:
- Historical curiosity: The only inverted scale to achieve governmental adoption
- Archival research: Russian meteorological data (1738-1840s) requires Delisle conversion
- Thermometer collecting: Delisle/Réaumur dual-scale antique thermometers from Russia
- Scientific history: Example of how methodology (cooling observation) shaped measurement design
Anders Celsius and the Original Scale (1742)
In 1742, Swedish astronomer Anders Celsius (1701–1744) proposed a temperature scale based on two fixed points related to water. However, his original scale was inverted from what we use today:
Celsius's original scale (1742):
- 0°: Boiling point of water
- 100°: Freezing point of water
This counterintuitive arrangement had water freezing at the higher number and boiling at the lower number. Celsius chose this orientation possibly because he was primarily interested in measuring cold temperatures in Sweden, making it convenient to have larger numbers for colder conditions.
Why inversion? Some historians believe Celsius wanted to avoid negative numbers when measuring cold Swedish winters. By setting freezing at 100°, he could measure winter temperatures as positive values above 100.
The Reversal: Modern Celsius Scale
Shortly after Celsius's death in 1744, the scale was reversed to its current form, where:
- 0°: Freezing point of water
- 100°: Boiling point of water
Who reversed it? Historical records are unclear, but credit is typically given to one or both:
- Carl Linnaeus (1707–1778): Swedish botanist who worked at Uppsala University with Celsius
- Jean-Pierre Christin (1683–1755): French physicist who independently proposed a similar reversed scale in 1743
The reversed scale proved more intuitive—negative numbers represent below-freezing temperatures, and positive numbers represent above-freezing, aligning with everyday experience.
From "Centigrade" to "Celsius" (1948)
For over 200 years, the scale was commonly known as "Centigrade," from the Latin words:
- "Centi": hundred
- "Grade": steps or degrees
The name described the scale's defining characteristic: 100 equal intervals between freezing and boiling.
The 1948 name change: In 1948, the 9th General Conference on Weights and Measures (CGPM) officially renamed the scale from "Centigrade" to "Celsius" for two important reasons:
- Honor Anders Celsius: Recognize the inventor's contribution to science
- Avoid confusion: The term "centigrade" was also used in French and Spanish to describe angular measurements (1/100th of a right angle), creating potential confusion in scientific contexts
The renaming standardized international terminology, making "Celsius" the official name in all languages and scientific literature.
Adoption into the Metric System (SI)
1954 - SI Integration: The 10th General Conference on Weights and Measures formally adopted Celsius into the International System of Units (SI) in 1954. Celsius was defined relative to the Kelvin scale:
- Kelvin: SI base unit for thermodynamic temperature
- Celsius: Derived unit, defined as K − 273.15
This integration meant Celsius became part of the coherent system of metric units used worldwide for science, engineering, and commerce.
1967-1968 - Definition refinement: The definition was refined to be based on the triple point of water (0.01°C, 273.16 K) rather than ice point and boiling point, providing a more precise scientific standard.
2019 - Modern definition: Following the 2019 redefinition of SI base units, the Kelvin (and thus Celsius) is now defined by fixing the Boltzmann constant, providing an even more fundamental and reproducible definition.
Global Adoption (20th Century)
Throughout the 20th century, Celsius adoption spread globally as countries adopted the metric system:
Early adopters (1790s-1800s):
- France and other European countries adopting metric system
- Gradual spread through scientific community
Mid-20th century (1960s-1980s):
- United Kingdom transitioned from Fahrenheit to Celsius (1960s-1970s)
- Canada adopted Celsius in 1975
- Australia, New Zealand adopted metric/Celsius (1960s-1970s)
- Most former British colonies transitioned to Celsius
Modern status:
- 190+ countries use Celsius as the official temperature scale
- 3 countries primarily use Fahrenheit: United States, Bahamas, Cayman Islands
- Universal in international aviation, shipping, science, and medicine
The US Exception
The United States remains the primary holdout, continuing to use Fahrenheit for:
- Weather forecasts
- Household thermostats
- Cooking temperatures (ovens, recipes)
- Public discourse
However, Celsius is used in US contexts:
- Scientific research (NASA, universities)
- Military
- Medical (increasingly, alongside Fahrenheit)
- International trade and diplomacy
Multiple attempts to convert the US to metric/Celsius (notably in the 1970s) have failed due to cultural resistance, conversion costs, and lack of political will.
Common Uses and Applications: degrees Delisle vs degrees Celsius
Explore the typical applications for both Delisle (imperial/US) and Celsius (metric) to understand their common contexts.
Common Uses for degrees Delisle
Historical Russian Meteorology (1738-1840s)
The primary application of the Delisle scale was Russian weather observation:
Imperial Meteorological Network:
- St. Petersburg Observatory: Daily temperatures recorded in Delisle
- Moscow weather stations: Imperial Academy network standardized on Delisle
- Siberian frontier posts: Military expeditions reported temperatures in Delisle
- Black Sea and Baltic ports: Naval meteorological data in Delisle
Record Keeping: Archives from this period contain:
- Handwritten logbooks with Delisle readings
- Published annual weather summaries
- Agricultural yield correlations with Delisle temperatures
- Military campaign weather reports (e.g., Napoleon's 1812 invasion)
18th-Century Russian Scientific Research
Russian Academy scientists used Delisle for:
Physics Experiments:
- Thermal expansion studies
- Phase transition research (freezing, melting, boiling)
- Instrument calibration standards
Biological Research:
- Plant growth temperature requirements
- Animal physiology studies
- Seed germination experiments
Astronomical Observations:
- Observatory temperature logs (affecting telescope precision)
- Atmospheric refraction corrections based on temperature
Historical Document Interpretation
Modern researchers encounter Delisle in:
Russian Imperial Archives:
- Government reports (1738-1840s)
- Military campaign records
- Agricultural survey data
- Medical records from Russian hospitals
Scientific Publications:
- Imperial Russian Academy journals
- European scientific correspondence with Russian researchers
- Exploration expedition reports (Bering, Kamchatka expeditions)
Literature and Personal Correspondence:
- Letters between Russian aristocracy
- Travel journals of European visitors to Russia
- Historical novels set in 18th-19th century Russia
Antique Thermometer Collecting
Delisle thermometers are rare and valuable collectibles:
Rarity Factors:
- Limited production period: 1732-1850s primarily
- Geographic concentration: Almost exclusively Russian Empire
- Destruction: Many lost during Russian Revolution, World Wars
- Dual-scale models: Delisle/Réaumur thermometers from 1780s-1840s most sought
Market Value:
- Original Delisle thermometers: $1,000-$10,000+ (extreme rarity)
- Dual-scale Delisle/Réaumur: $800-$5,000 (more common)
- Reproductions/modern curiosities: $50-$200
Education and Science Museums
Science museums use Delisle thermometers to teach:
- History of measurement: Evolution of temperature scales
- Scientific methodology: How observation shapes measurement design
- Cultural context: Russian Empire's scientific development
- Inverted scales: Challenging students' assumptions about "hotter = higher number"
Online Temperature Converters
Delisle appears in comprehensive temperature conversion tools:
- Historical conversion calculators for archival research
- "Exotic scales" demonstrations alongside Rømer, Newton scales
- Educational tools teaching temperature scale diversity
When to Use degrees Celsius
The Celsius scale is the standard temperature measurement in nearly all countries except the United States, and is used extensively across all fields:
1. Weather and Meteorology
The primary temperature scale for weather forecasts, climate data, and meteorological reports worldwide. All international weather organizations use Celsius as the standard.
Weather reporting:
- Daily forecasts (high/low temperatures)
- Heat warnings (above 30-35°C)
- Freeze warnings (below 0°C)
- Wind chill calculations
- Heat index calculations
Climate science:
- Historical temperature records
- Climate change monitoring
- Sea surface temperature measurements
- Atmospheric temperature profiles
- Glacial and polar ice monitoring
Common Conversions:
- Celsius to Fahrenheit (for US weather reports)
- Celsius to Kelvin (for scientific weather data)
2. Domestic and Everyday Use
Daily temperature measurements including thermostats, air conditioning units, water heaters, and personal thermometers in all metric countries.
Household applications:
- Home heating thermostat settings (18-22°C)
- Air conditioning settings (22-24°C)
- Water heater temperature (50-60°C)
- Refrigerator temperature (4°C)
- Freezer temperature (-18°C)
- Baby bath water (37°C)
- Laundry water temperatures (cold, 30°C, 40°C, 60°C, 90°C)
3. Science and Research
Universal standard in scientific research alongside Kelvin. Used in chemistry, biology, physics, earth sciences, and engineering for temperature measurements and calculations.
Why Scientists Use Celsius:
- Easy conversion to Kelvin (K = °C + 273.15)
- Intuitive water-based reference points
- Decimal-based like other SI units
- International standardization
- Direct relationship to Kelvin (1°C = 1 K difference)
Scientific applications:
- Chemical reactions and kinetics
- Material testing and properties
- Biological experiments and incubation
- Environmental monitoring
- Quality control testing
4. Medical and Healthcare
Standard for body temperature measurements, medical equipment calibration, pharmaceutical storage requirements, and clinical guidelines worldwide.
Medical Temperature Guidelines:
- Normal body temperature: 36.5-37.5°C
- Fever threshold: Above 38°C
- Hypothermia risk: Below 35°C
- Hyperthermia emergency: Above 40°C
- Vaccine storage: 2-8°C (refrigerated) or -20°C (frozen)
Medical equipment:
- Digital thermometers
- Incubators and warmers
- Sterilization equipment (autoclaves at 121°C or 134°C)
- Laboratory analyzers
- Blood storage (4°C for whole blood, -80°C for plasma)
Convert medical temperatures with our temperature converter.
5. Culinary and Food Safety
Used for cooking instructions, food storage, and safety guidelines in most countries. Recipe books, ovens, and cooking appliances display temperatures in Celsius.
Food Safety Temperatures:
- Danger zone: 5-60°C (41-140°F) - bacteria multiply rapidly
- Refrigeration: 0-4°C (32-39°F)
- Freezing: -18°C (0°F) or below
- Safe minimum cooking: 75°C (167°F) for most foods
- Poultry: 75°C (167°F) internal temperature
- Ground meat: 71°C (160°F) internal temperature
Common Oven Settings:
- Slow/Low: 120-150°C (248-302°F)
- Moderate: 160-180°C (320-356°F)
- Standard: 180-200°C (356-392°F)
- Hot: 200-230°C (392-446°F)
- Very Hot: 230-250°C (446-482°F)
Use our Celsius to Fahrenheit converter for recipe conversions.
6. HVAC and Climate Control
Standard unit for heating, ventilation, and air conditioning systems in commercial and residential buildings worldwide.
Climate control:
- Programmable thermostats
- Central heating systems
- Air conditioning units
- Heat pumps
- Industrial climate control
- Data center cooling
7. Education
Taught as the primary temperature scale in schools worldwide as part of the metric system curriculum.
Educational contexts:
- Elementary science (water freezing/boiling)
- Chemistry (reaction temperatures)
- Physics (thermodynamics)
- Biology (optimal growth temperatures)
- Geography (climate zones)
8. Aviation and Transportation
International aviation uses Celsius for temperature reporting, along with other metric units.
Aviation applications:
- Outside air temperature (OAT)
- Engine temperature monitoring
- Cargo hold temperature
- De-icing temperature thresholds
- Weather reporting at airports (METAR/TAF)
9. Agriculture and Horticulture
Plant growth:
- Optimal growing temperatures (species-specific)
- Germination temperatures
- Greenhouse climate control
- Frost protection thresholds (below 0°C)
Livestock:
- Barn and shelter temperature monitoring
- Incubation temperatures (poultry)
- Heat stress thresholds
Additional Unit Information
About Delisle (°De)
What are the freezing and boiling points of water in Delisle?
Water boils at 0°De and freezes at 150°De. This is inverted compared to all other major temperature scales (Celsius, Fahrenheit, Réaumur, Kelvin), where higher numbers indicate hotter temperatures.
Why does the Delisle scale decrease with increasing temperature?
Delisle's methodology determined the scale's direction:
- Calibration process: He started with boiling water (100°C) as his zero reference point
- Cooling observation: He watched mercury contract as water cooled from boiling
- Counting contraction: Each unit of contraction represented one Delisle degree
- Result: At freezing point, the mercury had contracted 150 divisions from boiling
The scale thus measured "degrees of cooling" from boiling water, making hotter temperatures numerically smaller. While counterintuitive, it reflected his experimental procedure.
How does Delisle relate to Celsius?
Conversion formulas:
- Delisle → Celsius: °C = 100 - (°De × 2/3)
- Celsius → Delisle: °De = (100 - °C) × 1.5
Relationship: Each Delisle degree = 2/3 Celsius degree (0.667°C), but running in opposite direction.
Example:
- 0°De = 100°C (boiling)
- 150°De = 0°C (freezing)
- 75°De = 50°C (midpoint)
The "100 -" in the formula accounts for the inversion.
Was the Delisle scale ever widely used?
Yes, in Imperial Russia (1738-1840s):
The Delisle scale was the official temperature standard of the Russian Empire for approximately one century. It was mandatory for:
- All government meteorological stations
- Imperial Russian Academy scientific research
- Military weather reporting
- Educational institutions
Not widely used elsewhere: Aside from Russia, Delisle remained a curiosity. Western Europe used Réaumur or Fahrenheit; Delisle was essentially a Russian phenomenon.
Why didn't other countries adopt the Delisle scale?
Several factors limited adoption:
- Counterintuitive: The inversion (hotter = lower number) confused users
- Late arrival: By 1732, Fahrenheit (1714) and Réaumur (1730) were established
- Geographic isolation: Russia's distance from Western European scientific centers
- Communication barriers: Language and political isolation limited dissemination
- No compelling advantage: The inversion offered no practical benefit over conventional scales
The scale succeeded in Russia due to Delisle's position at the Imperial Academy and government decree, not scientific merit.
How do you convert a Delisle temperature to Fahrenheit?
Two-step method:
- Convert Delisle to Celsius: °C = 100 - (°De × 2/3)
- Convert Celsius to Fahrenheit: °F = (°C × 9/5) + 32
Direct formula: °F = 212 - (°De × 6/5) or °F = 212 - (°De × 1.2)
Example: 120°De (Russian "room temperature")
- Step 1: °C = 100 - (120 × 2/3) = 100 - 80 = 20°C
- Step 2: °F = (20 × 1.8) + 32 = 36 + 32 = 68°F
Direct: 212 - (120 × 1.2) = 212 - 144 = 68°F ✓
Can you still find Delisle thermometers?
Original antiques: Extremely rare and valuable
- Russian-made Delisle thermometers (1738-1850): $1,000-$10,000+
- Dual-scale Delisle/Réaumur (1780-1840): $800-$5,000
- Most survive in Russian museums, private collections, or academic institutions
Modern reproductions: Very limited availability
- Some specialty scientific instrument makers produce educational replicas
- Mostly for museum exhibits or science education purposes
- Generally not commercially available
Why so rare:
- Short production period (≈110 years)
- Limited geographic area (Russian Empire only)
- Wars and revolutions destroyed many (1812, 1917, WWII)
- Glass fragility means few survived intact
What does negative Delisle mean?
Negative Delisle = Above boiling point (>100°C):
Since 0°De = 100°C (boiling), temperatures above boiling would be negative:
- -15°De = 110°C (230°F) - pressurized water
- -30°De = 120°C (248°F) - autoclave sterilization
- -150°De = 200°C (392°F) - hot oven
Rarely used: Delisle's original design focused on ambient and cooling temperatures. High-temperature applications were uncommon in 18th-century Russia, so negative Delisle values are virtually absent from historical records.
How do historians handle Russian weather data in Delisle?
Conversion workflow:
- Identify Delisle readings in archival documents (e.g., "180 градусов Делиля" = 180 degrees Delisle)
- Apply conversion formula: °C = 100 - (180 × 2/3) = 100 - 120 = -20°C
- Convert to Fahrenheit if needed: (-20 × 1.8) + 32 = -4°F
- Document both original and converted values for scholarly accuracy
Example from historical record:
- Original: "Санкт-Петербург, 15 января 1740, 195°De" (St. Petersburg, January 15, 1740, 195°De)
- Conversion: 100 - (195 × 2/3) = 100 - 130 = -30°C = -22°F (severe cold)
Why is Delisle important to the history of science?
Scientific significance:
- Methodological diversity: Demonstrates how experimental procedure shaped measurement design
- Governmental standardization: First empire-wide temperature scale adoption (1738)
- Cultural context: Reflects Russian Empire's scientific modernization under Peter the Great's legacy
- Measurement evolution: Shows the pre-standardization diversity of temperature scales
- Unique inversion: Only inverted scale to achieve widespread official use
Lessons:
- Measurement standards require international consensus, not just local adoption
- Intuitive design matters for widespread acceptance
- Historical contingency (Delisle's Academy position) can temporarily override scientific merit
Are there any other inverted temperature scales?
No other major inverted scales achieved significant use.
Minor historical attempts:
- Some early thermometers were calibrated from hot to cold simply due to construction methods
- Individual scientists occasionally created personal inverted scales for specific experiments
Why Delisle is unique:
- Only inverted scale adopted by a government (Imperial Russia, 1738)
- Only inverted scale used for over a century
- Only inverted scale with substantial archival presence
All other successful temperature scales (Fahrenheit, Celsius, Réaumur, Kelvin, Rankine) use conventional orientation where higher numbers = hotter.
About Celsius (°C)
Is Celsius the same as Centigrade?
Yes, 'Celsius' and 'Centigrade' refer to the same temperature scale.
History of the name:
- 1742-1948: Called "Centigrade" (from Latin: "centum" = hundred, "gradus" = steps)
- 1948: Officially renamed "Celsius" by the 9th General Conference on Weights and Measures
Reasons for the change:
- Honor Anders Celsius: Recognize the inventor's contribution
- Avoid confusion: "Centigrade" was also used for angular measurements (1/100th of a right angle), causing confusion in French and Spanish scientific literature
Modern usage: "Celsius" is the official and preferred term worldwide, though "Centigrade" is still occasionally heard, especially among older generations.
How does Celsius relate to Kelvin?
The Celsius scale is defined relative to the Kelvin scale, the SI base unit for thermodynamic temperature.
Key relationships:
- K = °C + 273.15 (Celsius to Kelvin)
- °C = K − 273.15 (Kelvin to Celsius)
- 1°C change = 1 K change (same interval size)
Differences:
- Zero points differ: 0°C = 273.15 K
- Kelvin is absolute: No negative values (0 K = absolute zero)
- Celsius is relative: Can be negative (negative values are below water's freezing point)
When to use which:
- Kelvin: Thermodynamics, gas laws, absolute temperature calculations
- Celsius: Everyday measurements, weather, cooking, most practical applications
Use our Celsius to Kelvin converter for instant conversions.
Why is Celsius used so widely?
Celsius is the global standard for several compelling reasons:
1. Intuitive reference points:
- 0°C = water freezes (ice formation)
- 100°C = water boils (steam formation)
- Water is fundamental to life, making these points universally relatable
2. Metric system integration:
- Decimal-based (base-10), like all metric units
- Easy to work with: 100 equal intervals
- Aligns with other SI units
3. Scientific convenience:
- Direct conversion to Kelvin (K = °C + 273.15)
- Same interval size as Kelvin (1°C = 1 K difference)
- International scientific standard
4. Global adoption:
- 190+ countries use Celsius officially
- International weather reporting
- Universal aviation standard
- Medical and healthcare standard
5. Simplicity:
- Negative temperatures = below freezing
- Positive temperatures = above freezing
- Easy to understand and remember
How do you convert Celsius to Fahrenheit quickly?
Quick mental math approximation:
- Multiply by 2
- Add 30
Examples:
- 20°C → (20 × 2) + 30 = 70°F (actual: 68°F, close!)
- 25°C → (25 × 2) + 30 = 80°F (actual: 77°F)
- 10°C → (10 × 2) + 30 = 50°F (actual: 50°F, exact!)
- 0°C → (0 × 2) + 30 = 30°F (actual: 32°F, within 2°)
Accuracy: Within 2-4°F for most common temperatures (0-30°C range)
For exact conversions:
- Formula: °F = (°C × 9/5) + 32
- Tool: Celsius to Fahrenheit converter
Memorize key points:
- 0°C = 32°F (freezing)
- 10°C = 50°F
- 20°C = 68°F
- 30°C = 86°F
- 37°C ≈ 98.6°F (body temperature)
What is a comfortable room temperature in Celsius?
Standard comfortable room temperature: 20-22°C (68-72°F)
Detailed comfort ranges:
- 16-18°C (61-64°F): Cool, good for sleeping
- 18-19°C (64-66°F): Comfortable with warm clothing
- 20-21°C (68-70°F): Ideal for most people during daytime activities
- 22-23°C (72-73°F): Warm and comfortable
- 24-25°C (75-77°F): Getting warm, may need cooling
- Above 26°C (79°F): Uncomfortably warm indoors
Factors affecting comfort:
- Humidity: Higher humidity feels warmer
- Air movement: Fans increase comfort
- Activity level: Exercise generates heat
- Clothing: More clothing allows lower temperatures
- Personal preference: Varies by individual
- Acclimatization: People adapt to local climates
Typical thermostat settings:
- Winter heating: 20°C (68°F)
- Summer cooling: 24°C (75°F)
- Energy savings: Lower in winter (18°C), higher in summer (26°C)
- Office standard: 21-22°C (70-72°F)
At what Celsius temperature does water boil at high altitude?
Water boils at lower temperatures at high altitude because atmospheric pressure decreases:
Boiling point by altitude:
- Sea level (0m): 100°C (212°F)
- 500m (1,640ft): ~98.5°C (209°F)
- 1,000m (3,281ft): ~97°C (207°F)
- 1,500m (4,921ft): ~95°C (203°F)
- 2,000m (6,562ft): ~93°C (199°F)
- 3,000m (9,843ft): ~90°C (194°F)
- 4,000m (13,123ft): ~87°C (189°F)
- 5,000m (16,404ft): ~83°C (181°F)
- 8,849m (29,032ft - Mt. Everest): ~71°C (160°F)
Rule of thumb: Water's boiling point decreases by approximately 1°C for every 300m (or 1°F per 500ft) increase in elevation.
Why this matters:
- Cooking times increase: Food takes longer to cook at lower boiling temperatures
- Pasta, rice, vegetables: May need extra time
- Baking adjustments: Recipes may need modification at high altitude
- Tea/coffee brewing: Lower temperature may affect flavor extraction
Is 20°C hot or cold?
20°C (68°F) is generally considered mild to comfortable—neither hot nor cold.
Context matters:
Indoor temperature:
- Perfect room temperature for most people
- Standard thermostat setting in many countries
- Comfortable for light clothing
Outdoor weather:
- Pleasant spring/fall day
- Light jacket or sweater may be comfortable
- Good weather for outdoor activities
Water temperature:
- Cool for swimming
- Tolerable for active swimming, cold for leisure
- Ocean/lake water at 20°C feels refreshing but cool
Sleeping:
- Slightly warm for optimal sleep
- Most people prefer 16-18°C (61-64°F) for sleeping
Cultural/regional perspectives:
- Tropical residents: May find 20°C cold
- Arctic residents: May find 20°C warm
- Temperate zone residents: Find it comfortable and pleasant
Humidity factor:
- 20°C with high humidity feels warmer
- 20°C with low humidity feels cooler
What temperature is dangerous for humans in Celsius?
Dangerously Cold (Hypothermia) - Body Temperature:
- Below 35°C (95°F): Hypothermia begins, shivering
- 32-35°C (89-95°F): Mild hypothermia, confusion, drowsiness
- 28-32°C (82-89°F): Moderate hypothermia, irregular heartbeat
- Below 28°C (82°F): Severe hypothermia, unconsciousness, life-threatening
- Below 24°C (75°F): Usually fatal
Dangerously Hot (Hyperthermia) - Body Temperature:
- 38°C (100.4°F): Fever/heat stress
- 39°C (102.2°F): Moderate fever
- 40°C (104°F): High fever, medical attention needed
- 41°C (105.8°F): Heat stroke risk, emergency
- 42°C (107.6°F): Critical, organ damage begins
- Above 43°C (109.4°F): Usually fatal without rapid cooling
Environmental Temperature Dangers:
Cold:
- Below -40°C (-40°F): Frostbite in minutes, exposed skin freezes
- -30 to -40°C (-22 to -40°F): Extreme cold, survival difficult
- -20 to -30°C (-4 to -22°F): Very cold, proper protection essential
- Below -10°C (14°F): Frostbite risk on exposed skin
Heat:
- Above 35°C (95°F): Heat stress risk, especially with high humidity
- 40-45°C (104-113°F): Heat exhaustion and heat stroke risk
- Above 50°C (122°F): Survival difficult without shade, water, and cooling
- Above 55°C (131°F): Extreme danger, few minutes of exposure can be fatal
Heat Index (temperature + humidity): High humidity makes temperatures feel hotter and increases danger—40°C with high humidity can be more dangerous than 45°C with low humidity.
Why do Americans use Fahrenheit instead of Celsius?
Historical reasons:
1. Early adoption (1720s):
- Fahrenheit scale invented in 1724 by Daniel Gabriel Fahrenheit
- Adopted in English-speaking world, including American colonies
- Celsius wasn't invented until 1742, after Fahrenheit was established
2. Independence (1776):
- US gained independence before metric system was developed (1790s)
- American infrastructure already built around British Imperial system
- No compelling reason to change at the time
3. Metric system resistance:
- France developed metric system in 1790s
- US chose not to adopt metric officially
- Multiple attempts to convert US to metric have failed (notably 1970s)
Cultural and practical reasons:
1. Cultural inertia:
- Generations of Americans learned Fahrenheit
- Emotional attachment to familiar measurements
- "If it ain't broke, don't fix it" mentality
2. Conversion costs:
- Enormous expense to convert infrastructure
- All weather stations, thermostats, ovens, road signs
- Industrial equipment, scientific instruments
- Education system overhaul needed
3. Perceived precision:
- Fahrenheit has smaller degree increments
- 1°F = 0.56°C (finer granularity)
- Some argue this is more precise for everyday use
Current status:
Fahrenheit domains (US):
- Weather forecasts
- Household thermostats
- Cooking temperatures (ovens)
- Public discourse
Celsius domains (US):
- Scientific research (NASA, universities)
- Military
- Medical (increasingly)
- International trade/diplomacy
Other Fahrenheit users: Only 3 countries primarily use Fahrenheit: United States, Bahamas, Cayman Islands. The rest of the world (190+ countries) uses Celsius.
Practical impact:
- Americans traveling abroad must learn Celsius
- International collaboration requires conversion
- Many Americans now learn both scales
- US is increasingly isolated in temperature measurement
Use our Fahrenheit to Celsius converter to easily switch between scales.
What is normal body temperature in Celsius?
Normal body temperature: 36.5-37.5°C (97.7-99.5°F)
Average: 37°C (98.6°F)
Important factors affecting body temperature:
1. Time of day:
- Morning (6 AM): Lower, around 36.3°C (97.3°F)
- Afternoon/Evening (6 PM): Higher, around 37.3°C (99.1°F)
- Daily variation: About 0.5-1°C difference
2. Measurement location:
- Rectal: 0.5°C (0.9°F) higher than oral (most accurate)
- Oral: Standard reference point
- Ear (tympanic): Similar to rectal if done correctly
- Armpit (axillary): 0.5°C (0.9°F) lower than oral (least accurate)
- Forehead (temporal): Convenient but less accurate
3. Age:
- Infants: Slightly higher (36.6-37.8°C / 97.9-100°F)
- Children: Similar to adults
- Elderly: May be slightly lower (35.8-36.9°C / 96.4-98.4°F)
4. Activity level:
- Rest: Lower baseline temperature
- Exercise: Can temporarily raise to 38-39°C (100-102°F)
- Digestion: Slightly raises temperature
5. Other factors:
- Menstrual cycle (women)
- Time since eating
- Ambient temperature
- Hydration status
- Circadian rhythm
Body temperature guide:
Below normal:
- Below 35°C (95°F): Hypothermia, medical concern
- 35-36°C (95-96.8°F): Mild hypothermia possible
- 36-36.5°C (96.8-97.7°F): Lower end of normal
Normal range:
- 36.5-37.5°C (97.7-99.5°F): Normal healthy range
- 37°C (98.6°F): Classic "normal" temperature (average)
Elevated/Fever:
- 37.5-38°C (99.5-100.4°F): Slightly elevated, monitor
- 38-39°C (100.4-102.2°F): Low-grade fever
- 39-40°C (102.2-104°F): Moderate fever, monitor closely
- Above 40°C (104°F): High fever, seek medical attention
Measurement best practices:
- Wait 30 minutes after eating/drinking/exercise before measuring
- Use same method consistently for comparison
- Digital thermometers most accurate for home use
- For infants: rectal measurement most reliable
How many degrees Celsius is freezing?
Water freezes at 0°C (32°F) at standard atmospheric pressure (sea level, 1 atmosphere).
What "freezing" means:
- 0°C: Temperature at which water transitions from liquid to solid (ice)
- Below 0°C: Water is solid (ice, snow)
- Above 0°C: Ice melts to liquid water
- Exactly 0°C: Water and ice can coexist in equilibrium
This is a defining point: The Celsius scale is specifically defined with 0°C as the freezing point of pure water, making it an intuitive and memorable reference.
Factors affecting freezing point:
1. Salinity:
- Pure water: 0°C (32°F)
- Seawater (~3.5% salt): ~-2°C (28°F)
- Saturated salt solution: ~-21°C (-6°F)
2. Pressure:
- Higher pressure: Slightly lowers freezing point
- Lower pressure: Slightly raises freezing point
- Effect is small: About -0.0075°C per atmosphere
3. Impurities/additives:
- Sugar: Lowers freezing point (ice cream stays soft)
- Alcohol: Significantly lowers freezing point (vodka freezes at -27°C)
- Antifreeze (ethylene glycol): Lowers to -37°C (50/50 mix)
- Road salt (calcium chloride): Melts ice down to -25°C
Weather context:
Freezing conditions:
- Below 0°C: Freezing, snow and ice form, water pipes at risk
- 0 to -5°C: Light freeze, frost forms overnight
- -5 to -10°C: Moderate freeze, icy roads
- Below -10°C: Hard freeze, outdoor activities limited
Near-freezing:
- 0-2°C: Just above freezing, frost possible
- 2-5°C: Cool, generally no freezing concerns
- 5-10°C: Cold but no freeze risk
Freezer temperatures:
- -18°C (0°F): Standard home freezer (well below freezing)
- -20°C (-4°F): Deep freeze
- -40°C (-40°F): Ultra-cold freeze (commercial/research)
Why 0°C matters:
- Frost warnings issued when temperature drops below 0°C
- Roads ice over below 0°C
- Outdoor water pipes freeze below 0°C
- Plants vulnerable to frost damage below 0°C
People Also Ask
How do I convert Delisle to Celsius?
To convert Delisle to Celsius, enter the value in Delisle in the calculator above. The conversion will happen automatically. Use our free online converter for instant and accurate results. You can also visit our temperature converter page to convert between other units in this category.
Learn more →What is the conversion factor from Delisle to Celsius?
The conversion factor depends on the specific relationship between Delisle and Celsius. You can find the exact conversion formula and factor on this page. Our calculator handles all calculations automatically. See the conversion table above for common values.
Can I convert Celsius back to Delisle?
Yes! You can easily convert Celsius back to Delisle by using the swap button (⇌) in the calculator above, or by visiting our Celsius to Delisle converter page. You can also explore other temperature conversions on our category page.
Learn more →What are common uses for Delisle and Celsius?
Delisle and Celsius are both standard units used in temperature measurements. They are commonly used in various applications including engineering, construction, cooking, and scientific research. Browse our temperature converter for more conversion options.
For more temperature conversion questions, visit our FAQ page or explore our conversion guides.
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All conversion formulas have been verified against international standards and authoritative sources to ensure maximum accuracy and reliability.
National Institute of Standards and Technology — International Temperature Scale standards
Bureau International des Poids et Mesures — Definition of the kelvin and temperature scales
Last verified: February 19, 2026