How many centimeters are in an inch?
1 in = 2.54 cm
An inch is exactly 0.0254 meters. Divide by 0.01 meters per centimeter: 0.0254 ÷ 0.01 = 2.54.
A meter is exactly 100 centimeters. Try the example button to check it.
Everyday measurements
Unit Converter
Convert length, mass, or temperature with clear units and a formula for your values.
Convert a measurement
Converted value
Enter a value and choose your units, then select Convert.
Your values are calculated in your browser and are not sent to a server.
Conversions you can check
How many kilograms are in a pound?
1 lb = 0.45359237 kg
This is the exact conversion for an avoirdupois pound. At 6 decimal places, the display is ≈ 0.453592 kg.
Choose 10 decimal places to see 0.4535923700 kg with no display rounding.
What is 32 °F in Celsius or kelvin?
32 °F = 0 °C = 273.15 K
First, (32 − 32) ÷ 1.8 = 0 °C. Add 273.15 to the Celsius value to get kelvin.
These formulas convert temperature readings. A temperature difference uses different offset rules.
Formulas and exact factors
For length and mass, the calculation is value × starting-unit factor ÷ destination-unit factor. Length factors are expressed in meters, and mass factors in kilograms. The table lists the exact factors used.
| Category | Unit | Exact equivalent |
|---|---|---|
| Length | Millimeters (mm) | 0.001 m |
| Length | Centimeters (cm) | 0.01 m |
| Length | Meters (m) | 1 m |
| Length | Kilometers (km) | 1000 m |
| Length | Inches (in) | 0.0254 m |
| Length | Feet (ft) | 0.3048 m |
| Length | Yards (yd) | 0.9144 m |
| Length | Miles (mi) | 1609.344 m |
| Mass | Milligrams (mg) | 0.000001 kg |
| Mass | Grams (g) | 0.001 kg |
| Mass | Kilograms (kg) | 1 kg |
| Mass | Ounces — mass (oz) | 0.028349523125 kg |
| Mass | Pounds (lb) | 0.45359237 kg |
Temperature uses offsets as well as scaling: °F = °C × 1.8 + 32, °C = (°F − 32) ÷ 1.8, and K = °C + 273.15. For Fahrenheit and kelvin directly, use K = (°F + 459.67) ÷ 1.8 or °F = K × 1.8 − 459.67.
Conversion references: NIST Handbook 44, Appendix C (PDF) provides customary and metric relationships; NIST’s temperature guide explains the temperature scales and exact conversions.
Common questions
Which feet, miles, pounds, and ounces does this use?
Feet and miles use international definitions: 1 ft = 0.3048 m and 1 mi = 1,609.344 m. Historical U.S. survey units are not included. Pounds and ounces are avoirdupois mass units: 16 oz = 1 lb. They are not troy ounces or fluid ounces. A fluid ounce measures volume and cannot be converted to mass without more information.
Why is a negative temperature sometimes rejected?
Celsius and Fahrenheit readings may be negative, but this converter rejects values below absolute zero: −273.15 °C, −459.67 °F, or 0 K. It converts absolute temperature readings, not temperature differences. For example, a rise of 10 °C corresponds to a rise of 18 °F, while a reading of 10 °C is 50 °F.
Does swapping units convert the previous result back?
No. Swap units exchanges the two unit selections and keeps your entered number unchanged. It clears the previous result. For example, entering 1 m to cm gives 100 cm; swapping the units sets up 1 cm to m. Rounded results are never copied into the input automatically.
How precise is the result?
Calculations use decimal arithmetic with 60 significant digits internally. Results display 6 decimal places by default, with choices of 0, 2, 4, 6, and 10. Exact halfway values round away from zero, trailing zeros are retained, and ≈ appears when display rounding changes the computed value. Some divisions repeat indefinitely; a finite display cannot show them exactly. The number of displayed digits does not establish the accuracy of your original measurement.
Which input formats are accepted?
Enter up to 15 digits before the decimal point and 10 after it, within 64 characters. Use a period for decimals and optional correctly grouped thousands commas, such as 1,234.5. Signed length and mass values are accepted, which can represent changes. Do not include units, expressions, or scientific notation. Each conversion stays within one category; currency and volume are outside this converter’s scope.