Centimeter (cm) - Unit Information & Conversion

Quick Answer: What is a Centimeter?

One centimeter equals one-hundredth of a meter (0.01 m) or approximately 0.394 inches. The centimeter is the standard unit for measuring body height, clothing sizes, and everyday objects in most countries worldwide. A standard credit card is about 8.5 cm wide, a typical smartphone is 14-16 cm tall, and rainfall is measured in centimeters. The centimeter bridges the gap between millimeters (too small for many purposes) and meters (too large for precision measurements), making it ideal for human-scale measurements.

Centimeter Comparison Table

From	To	Relationship
1 centimeter	millimeters	10 mm
1 centimeter	meters	0.01 m
1 centimeter	inches	0.393701 inches
1 centimeter	feet	0.0328084 feet
1 centimeter	kilometers	0.00001 km
1 inch	centimeters	2.54 cm (exactly)
1 foot	centimeters	30.48 cm
1 meter	centimeters	100 cm
10 millimeters	centimeters	1 cm

Definition

The centimeter (symbol: cm) is a unit of length equal to exactly one-hundredth of a meter (1/100 m or 0.01 m). It's also equal to exactly 10 millimeters.

The centimeter is part of the International System of Units (SI) and uses the metric prefix "centi-" meaning one-hundredth (from Latin centum, "hundred").

Mathematical Relationships

1 centimeter equals:

• 10 millimeters (mm)
• 0.01 meters (m)
• 0.00001 kilometers (km)
• 0.393701 inches (in)
• 0.0328084 feet (ft)

Key conversion:

• 1 inch = 2.54 cm exactly (this is the official international definition established in 1959)

Why Centimeters?

While the meter is the official SI base unit for length, centimeters are more practical for everyday measurements:

Too small for meters, too large for millimeters: A person who is 1.75 meters tall is more commonly described as 175 centimeters in metric countries. Writing "1.75 m" requires decimals; "175 cm" uses whole numbers.

Human-scale convenience: Most objects people interact with daily—clothing, screens, body measurements, food items—fall naturally into the 1-100 cm range.

Avoids decimal confusion: "15.2 cm" is clearer than "0.152 m" for most people.

History

French Revolution and the Birth of the Metric System

1790s: Revolutionary Innovation: The centimeter was born from the French Revolution's ambition to create a rational, universal measurement system based on nature and decimal mathematics.

The Meter Foundation: In 1791, the French Academy of Sciences defined the meter as one ten-millionth (1/10,000,000) of the distance from the equator to the North Pole along the meridian passing through Paris. The centimeter automatically followed as 1/100 of this meter.

Latin Roots: The prefix "centi-" derives from the Latin centum (hundred), making "centimeter" literally "hundredth of a meter."

1795 Official Adoption: France officially adopted the metric system on April 7, 1795, including the centimeter as a standard subdivision of the meter.

CGS System: The Centimeter's Scientific Era

1874: The Centimeter-Gram-Second System: British scientists James Clerk Maxwell and William Thomson (Lord Kelvin) promoted the CGS system, which used:

• Centimeter for length (instead of meter)
• Gram for mass (instead of kilogram)
• Second for time

Scientific Dominance: The CGS system became the preferred standard for physics and chemistry throughout the late 19th and early 20th centuries. Many scientific formulas and units were developed using centimeters.

Legacy Units: Several units still reflect the CGS heritage:

• Poise (viscosity): measured in gram/(centimeter·second)
• Erg (energy): gram·centimeter²/second²
• Gauss (magnetic field): CGS unit for magnetic flux density

Transition to SI and the Modern Era

1960: The SI System: The International System of Units (SI) was officially established, promoting the meter-kilogram-second (MKS) system instead of CGS.

Centimeter's Continued Relevance: Despite the official SI preference for meters, centimeters remained dominant for everyday measurements because:

• They're more practical for human-scale objects
• They avoid decimals for most common measurements
• They're familiar and intuitive

Global Adoption: Today, 195 of 198 countries use the metric system, with centimeters as the standard for body height, clothing, and everyday measurements. Only the United States, Myanmar, and Liberia officially use non-metric systems.

Real-World Examples: What Does a Centimeter Look Like?

Visual Reference Objects

Fingernail Width: The width of an adult's fingernail is approximately 1 centimeter.

Pencil Eraser: The diameter of a standard pencil eraser is about 0.6-0.7 cm.

AAA Battery Diameter: Approximately 1.05 cm.

Stacked Coins: A US penny is 1.9 cm in diameter; stacking 5 pennies gives about 1 cm of height.

Credit Card Thickness: About 0.08 cm (0.8 mm), so 12-13 credit cards stacked equals about 1 cm.

Body Measurements

Height in Centimeters (typical ranges):

• Newborn baby: 45-55 cm
• 1-year-old child: 70-80 cm
• 5-year-old child: 105-115 cm
• 10-year-old child: 130-145 cm
• Average adult woman: 160-165 cm (5'3"-5'5")
• Average adult man: 175-180 cm (5'9"-5'11")
• Tall adult: 190+ cm (6'3"+)

Other Body Measurements:

• Hand width (across palm): 7-9 cm
• Foot length: 24-28 cm (adults)
• Arm span: approximately equal to height
• Waist circumference: 70-100 cm (typical adult range)

Technology and Screens

Smartphone Dimensions:

• Width: 6-8 cm
• Height: 13-16 cm
• Thickness: 0.7-0.9 cm
• Screen diagonal: 12-17 cm (5-7 inches)

Tablet Screens:

• iPad (10.2"): approximately 20 cm × 25 cm
• Large tablets: 25-30 cm diagonal

Laptop Screens (measured diagonally):

• 13-inch: 33 cm diagonal
• 15-inch: 38 cm diagonal
• 17-inch: 43 cm diagonal

TV Screens (measured diagonally):

• 32-inch TV: 81 cm
• 55-inch TV: 140 cm
• 65-inch TV: 165 cm

Monitor Bezels: Modern monitors have bezels (frame edges) of 0.5-2 cm width.

Clothing and Fashion

Clothing Measurements (in cm):

• Shirt collar size: 38-45 cm circumference
• Chest measurement: 85-110 cm
• Waist measurement: 70-100 cm
• Inseam (pants): 70-85 cm
• Dress length: 90-110 cm (knee-length to midi)

European Shoe Sizes: Based on foot length in centimeters:

• EU 38 (US Women's 7): 24 cm
• EU 40 (US Women's 9): 25 cm
• EU 42 (US Men's 8.5): 26.5 cm
• EU 44 (US Men's 10): 28 cm

Fabric and Sewing:

• Seam allowance: 1.5 cm standard
• Hem depth: 3-5 cm typical
• Button diameter: 1-2.5 cm

Weather and Climate

Rainfall Measurement: Most countries report rainfall in millimeters or centimeters:

• Light rain: 0.1-0.5 cm per day
• Moderate rain: 0.5-2 cm per day
• Heavy rain: 2-5 cm per day
• Very heavy rain: 5+ cm per day

Snowfall: Often measured in centimeters:

• Light dusting: 1-3 cm
• Moderate snow: 5-15 cm
• Heavy snow: 15-30 cm
• Major snowstorm: 30+ cm

Hail Size: Small hail is 0.5-1 cm; large damaging hail can be 3-5 cm or more.

Food and Cooking

Pizza Sizes (diameter):

• Personal pizza: 20 cm (8 inches)
• Medium pizza: 30 cm (12 inches)
• Large pizza: 35-40 cm (14-16 inches)

Baking Pan Dimensions:

• Square cake pan: 20×20 cm or 23×23 cm
• Rectangular pan: 23×33 cm (9×13 inches)
• Round cake pan: 20 cm or 23 cm diameter

Food Items:

• Hot dog length: 15 cm
• Banana length: 15-20 cm
• Bread slice thickness: 1-1.5 cm
• Steak thickness: 2-3 cm (medium cut)

Common Uses

Medical and Healthcare

Growth Charts: Children's height is tracked in centimeters from birth:

• Pediatricians plot growth on percentile charts
• Birth length recorded in cm (typically 45-55 cm)
• Annual height measurements track development

Medical Measurements:

• Wound size: "3 cm laceration"
• Tumor diameter: measured in cm for staging
• Organ size: "enlarged liver extending 4 cm below rib cage"
• Dilation during childbirth: measured in cm (0-10 cm)

Medical Equipment:

• Blood pressure cuff width: 12-13 cm for adults
• Surgical incision length: documented in cm
• Catheter diameter: measured in mm, length in cm

Education and School Supplies

Rulers and Measuring Tools: Most rulers worldwide show centimeters:

• Standard ruler: 15 cm or 30 cm length
• Meter stick: 100 cm with cm markings
• Tape measures: marked in cm (and meters)

Paper Sizes (International ISO 216 Standard):

• A4 paper: 21 × 29.7 cm (most common worldwide)
• A5 paper: 14.8 × 21 cm (half of A4)
• A3 paper: 29.7 × 42 cm (double A4)
• Letter size (US): 21.6 × 27.9 cm (8.5 × 11 inches)

School Supplies:

• Pencil length: 19 cm (new)
• Notebook width: 15-21 cm
• Eraser length: 4-6 cm

Construction and Home Improvement

Tile Sizes: Floor and wall tiles measured in cm:

• Small tiles: 10×10 cm
• Medium tiles: 30×30 cm
• Large format tiles: 60×60 cm or 80×80 cm
• Subway tiles: 7.5×15 cm

Furniture Dimensions:

• Coffee table height: 40-50 cm
• Dining table height: 75 cm (standard)
• Chair seat height: 45-50 cm
• Sofa seat depth: 50-60 cm

Door Measurements:

• Standard interior door width: 80-90 cm
• Standard door height: 200-210 cm
• Door thickness: 3.5-4.5 cm

Art, Design, and Photography

Photo Print Sizes:

• 10×15 cm (4×6 inches) - standard print
• 13×18 cm (5×7 inches)
• 20×25 cm (8×10 inches)
• 30×40 cm (12×16 inches)

Canvas and Frame Sizes: Art supply stores sell in metric:

• Small canvas: 20×25 cm
• Medium canvas: 30×40 cm
• Large canvas: 50×70 cm

Drawing and Design:

• Technical drawings: dimensioned in cm or mm
• Graph paper: 0.5 cm or 1 cm grids
• Architectural scales: often use 1:50 or 1:100 (cm-based)

Sports and Recreation

Swimming Pool Depth: Measured in cm or meters:

• Shallow end: 90-120 cm
• Deep end: 180-300 cm
• Competition pool depth: minimum 200 cm

Bicycle Frame Sizes: Road bikes measured in cm:

• Small frame: 48-52 cm
• Medium frame: 54-56 cm
• Large frame: 58-62 cm

Sports Equipment:

• Tennis ball diameter: 6.5-6.7 cm
• Golf ball diameter: 4.3 cm
• Basketball diameter: 24 cm

Conversion Mistakes to Avoid

1. Rounding 2.54 cm per Inch

Mistake: "1 inch equals about 2.5 cm"

Problem: The correct value is 2.54 cm exactly. Rounding to 2.5 introduces a 1.6% error that compounds quickly.

Correct:

• 1 inch = 2.54 cm exactly
• 10 inches = 25.4 cm (not 25 cm)
• 6 feet (72 inches) = 182.88 cm (not 180 cm)

Practical impact: Someone who is 5'10" (70 inches) is 177.8 cm, not 175 cm—that's 2.8 cm of error (about 1 inch).

2. Forgetting to Multiply by 100 for Meter Conversions

Mistake: "1.75 meters equals 1.75 centimeters"

Problem: Forgetting to multiply by 100 when converting meters to centimeters.

Correct:

• 1 meter = 100 cm (not 1 cm)
• 1.75 meters = 175 cm (not 1.75 cm)
• 0.5 meters = 50 cm (not 0.5 cm)

Memory aid: The prefix "centi-" means 1/100, so multiply by 100 going from meters to centimeters.

3. Confusing Centimeters with Millimeters

Mistake: Using cm when mm is meant, or vice versa

Problem: Centimeters and millimeters differ by a factor of 10, leading to 10× errors.

Correct:

• 1 cm = 10 mm
• 5 cm = 50 mm (not 5 mm)
• 25 mm = 2.5 cm (not 25 cm)

When it matters: Technical drawings, engineering specs, precision manufacturing—always check the units!

4. Height Conversion Between Feet/Inches and Centimeters

Mistake: Converting feet to cm without converting inches first

Problem: "5 feet 10 inches = 5.1 feet" → incorrect intermediate conversion

Correct method:

1. Convert total height to inches: 5'10" = (5×12) + 10 = 70 inches
2. Multiply by 2.54: 70 × 2.54 = 177.8 cm

Common heights:

• 5'0" = 152.4 cm
• 5'6" = 167.6 cm
• 6'0" = 182.9 cm
• 6'6" = 198.1 cm

5. Waist Size Confusion

Mistake: Assuming clothing sizes are the same in inches and cm

Problem: A "32-inch waist" is not the same as a "32 cm waist"

Correct:

• 32-inch waist = 81.3 cm
• 34-inch waist = 86.4 cm
• 36-inch waist = 91.4 cm

When it matters: Online shopping, international clothing sizes, tailoring

6. TV and Monitor Screen Sizes

Mistake: Converting diagonal screen inches to cm without the 2.54 multiplier

Problem: Guessing conversions or using wrong factors

Correct:

• 24-inch monitor = 61 cm diagonal
• 32-inch TV = 81 cm diagonal
• 55-inch TV = 140 cm diagonal
• 65-inch TV = 165 cm diagonal

Note: Screens are always measured diagonally, not width or height.

Unit Frequently Asked Questions

How many centimeters are in a meter?

Exactly 100 centimeters in 1 meter. This is the defining relationship—the prefix "centi-" means one-hundredth (1/100).

Quick conversions:

• 1 meter = 100 cm
• 0.5 meters = 50 cm
• 2 meters = 200 cm
• 1.75 meters = 175 cm

Memory aid: Think "cent" as in "century" (100 years) or "cent" (1/100 of a dollar). One meter equals 100 centimeters just like one dollar equals 100 cents.

How many centimeters are in an inch?

Exactly 2.54 centimeters in 1 inch. This is the internationally agreed definition from the 1959 international yard and pound agreement.

Useful conversions:

• 1 inch = 2.54 cm
• 1 foot (12 inches) = 30.48 cm
• 1 yard (36 inches) = 91.44 cm

Reverse conversion:

• 1 cm = 0.393701 inches
• 10 cm ≈ 3.94 inches (about 4 inches)

What does 'centi' mean in centimeter?

The prefix "centi-" means one-hundredth (1/100). It comes from the Latin word centum, meaning "hundred."

Other metric prefixes using Latin numbers:

• Milli- (1/1,000) - from mille (thousand)
• Deci- (1/10) - from decem (ten)
• Centi- (1/100) - from centum (hundred)

Common uses of "centi-":

• Centimeter = 1/100 of a meter
• Centiliter = 1/100 of a liter
• Cent = 1/100 of a dollar
• Century = 100 years
• Centipede = "hundred feet" (Latin centum + pes)

How do I convert my height from feet/inches to centimeters?

Step-by-step process:

1. Convert to total inches: Multiply feet by 12, then add remaining inches
2. Multiply by 2.54: This converts inches to centimeters

Example: 5 feet 9 inches to centimeters

• Step 1: (5 × 12) + 9 = 60 + 9 = 69 inches
• Step 2: 69 × 2.54 = 175.26 cm

Common height conversions:

• 5'0" = 152 cm
• 5'3" = 160 cm
• 5'6" = 168 cm
• 5'9" = 175 cm
• 6'0" = 183 cm
• 6'3" = 191 cm

Is centimeter or millimeter more common?

It depends on the context:

Centimeters are more common for:

• Body height and measurements
• Clothing sizes
• Everyday objects
• Room dimensions
• Furniture
• Screen sizes
• Most consumer products

Millimeters are more common for:

• Precision engineering
• Manufacturing tolerances
• Small hardware (screws, bolts)
• Rainfall measurement
• Technical drawings
• Very small objects
• Scientific measurements

General rule: If it fits comfortably in the 1-100 range in centimeters, use cm. If it's very small or requires precision, use mm.

Why doesn't the US use centimeters?

The US officially uses inches, feet, and miles from the US customary system (derived from British imperial units). However, centimeters are increasingly common in the US for:

Where Americans DO use centimeters:

• Medical measurements (wound size, dilation, growth charts)
• Scientific research and laboratories
• Photography (focal lengths, sensor sizes)
• International trade
• Some technology specs (especially phones, computers)

Why the US hasn't fully converted:

• Infrastructure investment: Millions of road signs, tools, construction materials based on inches/feet
• Cultural familiarity: Generations raised with imperial units
• Economic cost: Expensive to replace or convert everything
• Lack of compelling reason: The system works for daily life; most Americans don't interact internationally enough to feel the inconvenience

The 1970s attempt: The Metric Conversion Act of 1975 encouraged voluntary metrication, but without mandatory adoption, change was minimal.

How tall is 180 cm in feet and inches?

180 cm = 5 feet 11 inches (more precisely, 5'10.87").

Conversion method:

1. Convert cm to inches: 180 ÷ 2.54 = 70.87 inches
2. Divide by 12 to get feet: 70.87 ÷ 12 = 5.906 feet
3. The decimal represents fractional feet: 0.906 × 12 = 10.87 inches
4. Result: 5 feet 10.87 inches, rounded to 5'11"

Common height conversions:

• 170 cm = 5'7"
• 175 cm = 5'9"
• 180 cm = 5'11"
• 185 cm = 6'1"
• 190 cm = 6'3"

What objects are about 1 centimeter?

Objects approximately 1 cm:

Width/diameter:

• Fingernail width (adult)
• Small button
• Pea diameter (7-9 mm, close to 1 cm)
• AAA battery diameter (10.5 mm)
• Pencil diameter (about 7 mm, close to 1 cm)

Thickness/height:

• Stack of 5 pennies
• Smartphone camera bump
• Pencil eraser height
• Standard die (10 mm = 1 cm)

Length:

• Small paperclip (about 2.5-3 cm, so 1 cm is roughly 1/3)
• Grain of rice length (about 0.6-0.7 cm)

How do centimeters relate to kilometers?

1 kilometer = 100,000 centimeters (or 1 cm = 0.00001 km)

Breakdown:

• 1 kilometer = 1,000 meters
• 1 meter = 100 centimeters
• Therefore: 1 km = 1,000 × 100 = 100,000 cm

Practical examples:

• Walking 1 km = moving 100,000 cm
• Marathon (42.195 km) = 4,219,500 cm
• 1 cm is a tiny fraction of a kilometer (0.001%)

When to use each:

• Centimeters: small objects, body measurements, precision work
• Meters: room dimensions, short distances, height of buildings
• Kilometers: travel distances, geographic measurements, road distances

Are centimeters used in clothing sizes?

Yes, extensively worldwide—except in the US and UK:

Europe and most of the world:

• Height: 170 cm, 180 cm, etc.
• Chest/bust: 85 cm, 90 cm, 95 cm
• Waist: 70 cm, 75 cm, 80 cm
• Inseam: 75 cm, 80 cm, etc.

Shoe sizes: European sizes are based on foot length in cm:

• EU 40 = 25 cm foot length
• EU 42 = 26.5 cm foot length

US and UK: Still primarily use inches for clothing measurements:

• 32-inch waist, 34-inch inseam, etc.
• However, many garments show both inches and centimeters on tags

International shopping tip: Always check size charts with centimeter measurements when buying from non-US retailers online.

How precise is a centimeter?

A centimeter provides moderate precision—suitable for most everyday measurements but not for high-precision work.

Centimeter precision is adequate for:

• Body height (±1 cm is acceptable)
• Clothing measurements
• Room dimensions
• General carpentry
• Everyday objects

Centimeter precision is insufficient for:

• Machining and manufacturing (uses millimeters or micrometers)
• Precision engineering (needs ±0.1 mm or better)
• Scientific experiments requiring high accuracy
• Electronics and circuit boards

Rule of thumb: If you need precision better than ±5 mm (0.5 cm), switch to millimeters or smaller units.

Quick Reference Card

Measurement	Value
1 centimeter equals	10 millimeters
	0.01 meters
	0.393701 inches
	0.0328084 feet
Key conversion	1 inch = 2.54 cm exactly
Common heights	160 cm = 5'3"
	175 cm = 5'9"
	183 cm = 6'0"
Visual reference	Width of adult fingernail ≈ 1 cm
Credit card	Width: 8.5 cm, Height: 5.4 cm
Smartphone	Width: 6-8 cm, Height: 13-16 cm
Prefix meaning	"Centi-" = one-hundredth (1/100)

Your Next Steps

Ready to convert centimeters to other length units? Use our centimeter converter:

• Convert centimeters to inches
• Convert centimeters to feet
• Convert centimeters to meters
• Convert centimeters to millimeters

Explore related units:

• Meter - The SI base unit (100 cm = 1 m)
• Millimeter - Smaller metric unit (10 mm = 1 cm)
• Inch - US/UK equivalent (1 inch = 2.54 cm)
• Kilometer - Longer distances (1 km = 100,000 cm)