UnitsConverter

Torr to Atmosphere Converter

Convert torr to atmospheres with our free online pressure converter.

Quick Answer

1 Torr = 0.001316 atmospheres

Formula: Torr × conversion factor = Atmosphere

Use the calculator below for instant, accurate conversions.

Our Accuracy Guarantee

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.

Last verified: February 2026Reviewed by: Sam Mathew, Software Engineer

Torr to Atmosphere Calculator

How to Use the Torr to Atmosphere Calculator:

  1. Enter the value you want to convert in the 'From' field (Torr).
  2. The converted value in Atmosphere will appear automatically in the 'To' field.
  3. Use the dropdown menus to select different units within the Pressure category.
  4. Click the swap button (⇌) to reverse the conversion direction.
Share:

How to Convert Torr to Atmosphere: Step-by-Step Guide

Converting Torr to Atmosphere involves multiplying the value by a specific conversion factor, as shown in the formula below.

Formula:

atm = Torr × 0.00131579

Example Calculation:

1 Torr = 0.001316 atm

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.

Not for professional use. Results should be verified before use in any critical application. View our Terms of Service for more information.

Need to convert to other pressure units?

View all Pressure conversions →
📊 Pressure Table

Print-friendly conversion reference

📋 Unit Symbols

Copy Torr & atm symbols

What is a Torr and a Atmosphere?

The Torr (symbol: Torr) is a unit of pressure based on an absolute scale. It is not an SI unit, but it is widely used in science and engineering.

The Modern Definition: 1 Torr is defined as exactly 1/760 of a standard atmosphere (1 atm).

Since a standard atmosphere is defined as exactly 101,325 Pascals (Pa), the exact value of one Torr is: 1 Torr = 101,325 / 760 Pascals ≈ 133.322368421 Pascals.

** Torr vs. mmHg**: Historically, the Torr was intended to be same as the millimeter of mercury (mmHg). However, because the density of mercury changes with temperature and local gravity varies across the Earth, the mmHg is not a "true" absolute unit. To solve this, the Torr was redefined as a fixed fraction of an atmosphere, making it a perfectly stable unit regardless of where or the temperature at which you measure it.

Key standard relationships:

  • 1 Torr = 1,000 milliTorr (mTorr)
  • 760 Torr = 1 standard atmosphere (atm)
  • 1 Torr ≈ 1.333 millibars (mbar)
  • 1 Torr ≈ 0.0193 PSI (pounds per square inch)

1 atm = 101,325 Pa = 101.325 kPa = 14.696 PSI = 1.01325 bar = 760 mmHg = 760 Torr = 29.92 inHg

Why "Atmosphere"?

The atmosphere unit is uniquely important because:

  • Defined exactly: CIPM (1954) set 1 atm = 101,325 Pa (exact)
  • Sea level reference: Based on average atmospheric pressure (not variable)
  • Universal constant: Used identically worldwide (unlike PSI or bar)
  • Chemistry standard: All chemistry/physics equations reference 1 atm conditions
  • STP baseline: "Standard Temperature and Pressure" = 0°C, 1 atm exactly

Note: The Torr is part of the imperial/US customary system, primarily used in the US, UK, and Canada for everyday measurements. The Atmosphere belongs to the imperial/US customary system.

History of the Torr and Atmosphere

: From the First Barometer to Modern Vacuums

The history of the Torr is the history of our understanding of the "void" and the air around us.

1. Evangelista Torricelli and the "Sea of Air" (1643)

Before the 1640s, scientists believed that "nature abhors a vacuum" and that space was always filled with something. Evangelista Torricelli, a student of Galileo, challenged this. He filled a glass tube with mercury and inverted it into a bowl. Instead of all the mercury flowing out, it stopped at a height of about 76 cm (760 mm).

Torricelli correctly deduced that it wasn't a "pull" from the vacuum at the top of the tube, but the weight of the atmosphere pushing down on the mercury in the bowl that held the liquid up. He famously stated: "We live submerged at the bottom of an ocean of elementary air."

2. The Birth of the Name (1913)

For centuries, pressure was simply measured in "inches of mercury" or "millimeters of mercury." In 1913, the unit was formally named the Torr to honor Torricelli.

3. The Great Redefinition (1954)

As science became more precise, the variance in mercury density became a problem (a "millimeter of mercury" in the Arctic was technically different from one at the Equator). In 1954, at the 10th General Conference on Weights and Measures, the Standard Atmosphere was fixed at exactly 101,325 Pascals. Consequently, the Torr was redefined as exactly 1/760 of that value, decoupling it from the physical properties of mercury forever.

Common Uses and Applications: torr vs atmospheres

Explore the typical applications for both Torr (imperial/US) and Atmosphere (imperial/US) to understand their common contexts.

Common Uses for torr

When to Use atmospheres

Chemistry: Gas laws (PV=nRT), reaction conditions, vapor pressures, standard conditions (STP).

  • Ideal Gas Law: P V = n R T (pressures typically in atm in chemistry)
  • Gas tables: Vapor pressures often given at 1 atm
  • STP (Standard Temperature & Pressure): Exactly 1 atm, 0°C (sometimes 25°C modern definition)

Diving: Depth pressure calculations (1 atm per 10m/33ft water).

  • Critical for: Decompression sickness risk, nitrogen narcosis, oxygen toxicity
  • Rule of thumb: Every 10 meters adds 1 atm pressure

Physics: Standard reference pressure for equations, thermodynamics.

  • Thermodynamics: Heat capacities typically defined at 1 atm
  • Boiling points: Water boils at 100°C only at 1 atm
  • Phase diagrams: Reference state for matter phase transitions

Engineering: High-pressure systems, pressure vessels, gas storage.

  • Vessel ratings: Designed for X psig over 1 atm ambient
  • Cylinder classifications: Based on working pressure as multiples of atm

Additional Unit Information

About Torr (Torr)

What is the difference between Torr and mmHg?

For almost all practical, medical, and industrial purposes, they are the same. However, scientifically:

  • Torr is defined as exactly 1/760 of a Standard Atmosphere (Standardized in 1954).
  • mmHg (millimeter of mercury) is based on the actual weight of liquid mercury, which changes slightly depending on gravity and temperature.
  • The difference is 1 part in 7 million. Unless you are building a particle accelerator, you can treat them as identical.

Why is Torr used in vacuum technology?

Torr is the preferred unit because most vacuum systems are based on pumping down from atmospheric pressure. Since 760 Torr is a standard atmosphere, it's very easy for an engineer to know how "far" they have to go. It also uses a logarithmic scale naturally, making it easy to talk about 10⁻⁶ or 10⁻⁹ Torr levels.

Is a Torr a "Metric" unit?

No. The official SI unit for pressure is the Pascal (Pa). However, because 1 Pascal is such a small amount of pressure (about the weight of a dollar bill on a table), scientists in specific fields prefer the Torr for convenience.

How do you convert Torr to PSI?

Multiply your Torr value by 0.0193368. Formula: PSI = Torr × 0.0193368 Example: 100 Torr ≈ 1.93 PSI.

What is a "milliTorr" (mTorr)?

Also known as a Micron, a milliTorr is 1/1,000th of a Torr. It is commonly used in "roughing" vacuum pumps (like the one in your school's physics lab or a high-end food sealer).

Is 0 Torr possible?

A "perfect" vacuum (exactly 0 Torr) is theoretically impossible according to quantum mechanics. Even in deep intergalactic space, there is a pressure of about 10⁻¹⁷ Torr due to a few stray hydrogen atoms and cosmic radiation.

Is Torr used in the medical field?

Yes, but doctors almost always call it mmHg. When a nurse says your blood pressure is "120 over 80," they are literally saying "120 Torr systolic and 80 Torr diastolic."

Who is the unit Torr named after?

It is named after Evangelista Torricelli, the Italian physicist who proved that air has weight and invented the mercury barometer in 1643.

How many Pascals are in a Torr?

Exactly 133.322368... Pascals. For most calculations, using 133.3 is sufficient.

What happens if you are exposed to 0 Torr?

This is "space vacuum." Contrary to movies, your head doesn't explode. However, the oxygen in your blood would diffuse out of your lungs into the vacuum, causing you to lose consciousness in about 15 seconds. Your skin is tough enough to hold "you" together, but you would swell up significantly as water in your tissues starts to turn to gas.

About Atmosphere (atm)

How many PSI is 1 atmosphere?

1 atm = 14.696 PSI (often rounded to 14.7 PSI)

Examples:

  • 2 atm = 29.4 PSI (10m dive depth)
  • 3 atm = 44.1 PSI (20m dive depth)
  • 10 atm = 147 PSI (compressed air)
  • 100 atm = 1,470 PSI (gas cylinder)

Atmosphere to PSI converter →

How many atmospheres in a bar?

1 bar = 0.986923 atm (approximately 1 atm, ~1.3% difference)

Conversion:

  • 1 atm = 1.01325 bar
  • 10 atm = 10.1325 bar
  • 100 atm = 101.325 bar
  • 200 atm = 202.65 bar (scuba tank)

Why different?: Bar defined as exactly 100,000 Pa; atm defined as 101,325 Pa.

Atmosphere to Bar converter →

What pressure is 2 atmospheres?

2 atm = 202,650 Pa = 202.65 kPa = 29.4 PSI = 2.026 bar = 1,520 mmHg

Physical meaning:

  • Diving 10 meters (33 feet) underwater
  • Absolute pressure at 10m depth
  • Double the surface atmospheric pressure
  • Pressure inside a pressure cooker

How do I calculate diving depth pressure?

Formula: Total Pressure (atm) = 1 + (Depth in meters ÷ 10)

Or: Total Pressure (atm) = 1 + (Depth in feet ÷ 33)

Examples:

  • 10m (33ft): 1 + (10÷10) = 2 atm
  • 20m (66ft): 1 + (20÷10) = 3 atm
  • 30m (99ft): 1 + (30÷10) = 4 atm
  • 40m (131ft): 1 + (40÷10) = 5 atm

Note: Freshwater calculation uses 10.3m; saltwater 10m per atmosphere.

What is STP in chemistry?

STP (Standard Temperature and Pressure):

  • Pressure: 1 atm = 101,325 Pa = 100 kPa (IUPAC uses 100 kPa)
  • Temperature: 0°C = 273.15 K

Purpose: Reference conditions for gas law calculations

Molar volume at STP: 22.414 L/mol (IUPAC: 22.711 L/mol at 100 kPa)

SATP (Standard Ambient):

  • Pressure: 1 atm = 101,325 Pa
  • Temperature: 25°C = 298.15 K
  • Molar volume: 24.465 L/mol

More commonly used in modern chemistry.

Conversion Table: Torr to Atmosphere

Torr (Torr)Atmosphere (atm)
0.50.001
10.001
1.50.002
20.003
50.007
100.013
250.033
500.066
1000.132
2500.329
5000.658
1,0001.316

People Also Ask

How do I convert Torr to Atmosphere?

To convert Torr to Atmosphere, enter the value in Torr in the calculator above. The conversion will happen automatically. Use our free online converter for instant and accurate results. You can also visit our pressure converter page to convert between other units in this category.

Learn more →

What is the conversion factor from Torr to Atmosphere?

The conversion factor depends on the specific relationship between Torr and Atmosphere. 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 Atmosphere back to Torr?

Yes! You can easily convert Atmosphere back to Torr by using the swap button (⇌) in the calculator above, or by visiting our Atmosphere to Torr converter page. You can also explore other pressure conversions on our category page.

Learn more →

What are common uses for Torr and Atmosphere?

Torr and Atmosphere are both standard units used in pressure measurements. They are commonly used in various applications including engineering, construction, cooking, and scientific research. Browse our pressure converter for more conversion options.

For more pressure conversion questions, visit our FAQ page or explore our conversion guides.

Helpful Conversion Guides

Learn more about unit conversion with our comprehensive guides:

📚 How to Convert Units

Step-by-step guide to unit conversion with practical examples.

🔢 Conversion Formulas

Essential formulas for pressure and other conversions.

⚖️ Metric vs Imperial

Understand the differences between measurement systems.

⚠️ Common Mistakes

Learn about frequent errors and how to avoid them.

View All Guides →

All Pressure Conversions

Pascal to KilopascalPascal to MegapascalPascal to HectopascalPascal to BarPascal to MillibarPascal to AtmospherePascal to Technical AtmospherePascal to TorrPascal to Millimeter of MercuryPascal to Inch of MercuryPascal to Pound per Square InchPascal to Kilopound per Square InchPascal to Kilogram-force per Square CentimeterPascal to Kilogram-force per Square MeterPascal to Millimeter of Water ColumnPascal to Inch of Water ColumnKilopascal to PascalKilopascal to MegapascalKilopascal to HectopascalKilopascal to BarKilopascal to MillibarKilopascal to AtmosphereKilopascal to Technical AtmosphereKilopascal to TorrKilopascal to Millimeter of MercuryKilopascal to Inch of MercuryKilopascal to Pound per Square InchKilopascal to Kilopound per Square InchKilopascal to Kilogram-force per Square CentimeterKilopascal to Kilogram-force per Square MeterKilopascal to Millimeter of Water ColumnKilopascal to Inch of Water ColumnMegapascal to PascalMegapascal to KilopascalMegapascal to HectopascalMegapascal to BarMegapascal to MillibarMegapascal to AtmosphereMegapascal to Technical AtmosphereMegapascal to TorrMegapascal to Millimeter of MercuryMegapascal to Inch of MercuryMegapascal to Pound per Square InchMegapascal to Kilopound per Square InchMegapascal to Kilogram-force per Square CentimeterMegapascal to Kilogram-force per Square MeterMegapascal to Millimeter of Water ColumnMegapascal to Inch of Water ColumnHectopascal to PascalHectopascal to KilopascalHectopascal to MegapascalHectopascal to BarHectopascal to MillibarHectopascal to AtmosphereHectopascal to Technical AtmosphereHectopascal to TorrHectopascal to Millimeter of MercuryHectopascal to Inch of MercuryHectopascal to Pound per Square InchHectopascal to Kilopound per Square InchHectopascal to Kilogram-force per Square CentimeterHectopascal to Kilogram-force per Square MeterHectopascal to Millimeter of Water ColumnHectopascal to Inch of Water ColumnBar to PascalBar to KilopascalBar to MegapascalBar to HectopascalBar to MillibarBar to AtmosphereBar to Technical AtmosphereBar to TorrBar to Millimeter of MercuryBar to Inch of MercuryBar to Pound per Square InchBar to Kilopound per Square InchBar to Kilogram-force per Square CentimeterBar to Kilogram-force per Square MeterBar to Millimeter of Water ColumnBar to Inch of Water ColumnMillibar to PascalMillibar to KilopascalMillibar to MegapascalMillibar to HectopascalMillibar to BarMillibar to AtmosphereMillibar to Technical AtmosphereMillibar to TorrMillibar to Millimeter of MercuryMillibar to Inch of MercuryMillibar to Pound per Square InchMillibar to Kilopound per Square InchMillibar to Kilogram-force per Square CentimeterMillibar to Kilogram-force per Square MeterMillibar to Millimeter of Water ColumnMillibar to Inch of Water ColumnAtmosphere to PascalAtmosphere to KilopascalAtmosphere to MegapascalAtmosphere to HectopascalAtmosphere to BarAtmosphere to MillibarAtmosphere to Technical AtmosphereAtmosphere to TorrAtmosphere to Millimeter of MercuryAtmosphere to Inch of MercuryAtmosphere to Pound per Square InchAtmosphere to Kilopound per Square InchAtmosphere to Kilogram-force per Square CentimeterAtmosphere to Kilogram-force per Square MeterAtmosphere to Millimeter of Water ColumnAtmosphere to Inch of Water ColumnTechnical Atmosphere to PascalTechnical Atmosphere to KilopascalTechnical Atmosphere to MegapascalTechnical Atmosphere to HectopascalTechnical Atmosphere to BarTechnical Atmosphere to MillibarTechnical Atmosphere to AtmosphereTechnical Atmosphere to Torr

Other Pressure Units and Conversions

Explore other pressure units and their conversion options:

View all pressure units →

Verified Against Authority Standards

All conversion formulas have been verified against international standards and authoritative sources to ensure maximum accuracy and reliability.

NIST Reference on Constants, Units and Uncertainty

National Institute of Standards and Technology — Fundamental physical constants and unit conversions

BIPM SI Units

Bureau International des Poids et Mesures — International System of Units (SI) definitions and standards

ISO 80000

International Organization for Standardization — Quantities and units international standards series

Last verified: February 19, 2026