Unit Converter — Length, Weight, Area, Volume

A two-way unit converter for seven categories, with exact definitions

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Value to convert

From unit

Converted value

To unit

1 cm = 0.3937007874 in

All units at once

Millimeter (mm)10
Centimeter (cm)1
Meter (m)0.01
Kilometer (km)0.00001
Inch (in)0.3937007874
Foot (ft)0.03280839895
Yard (yd)0.01093613298
Mile (mi)0.000006213711922
Nautical mile (nmi)0.000005399568035

Exact definitions are used: 1 in = 2.54 cm, 1 lb = 0.45359237 kg, 1 pyeong = 400/121 m² (about 3.305785 m²).

What it is

Recipes in cups, a TV sold in inches, a package weighed in pounds, a flight speed in knots: everyday life keeps asking for conversions between unit systems. This converter handles seven categories in one place: length, mass, area, volume, temperature, speed and data size. Type a number in either field and the other one is calculated at once. Under the result, a table shows the same quantity in every unit of the category, which is handy when you are not sure which unit you need.

How to use

Pick a category from the row at the top. The Pyeong ↔ m² button jumps straight to the Korean floor-area conversion.
Enter a value on the left and choose the units. The converted value appears on the right. You can type on the right side as well.
Press ⇄ to swap the two units.
Copy the equation with the button next to the result, and use the table below for other units.

How it works

Exact definitions: 1 in = 2.54 cm, 1 ft = 0.3048 m, 1 mi = 1,609.344 m, 1 lb = 0.45359237 kg, 1 US gallon = 3.785411784 L, and 1 pyeong = 400/121 m².
Linear units: the value is converted to the category’s base unit (m, kg, m², L, m/s, byte) and divided by the target unit’s size.
Temperature: Celsius is the middle step. Fahrenheit uses (°F − 32) × 5/9 and Kelvin uses K − 273.15. A warning appears if you go below absolute zero.
Data size: KB, MB, GB and TB are powers of 1,000; KiB, MiB, GiB and TiB are powers of 1,024. One byte is 8 bits.
Volume: cups, spoons, pints, quarts and gallons are US customary units.
Display: floating-point noise is removed at 12 significant digits and up to 10 are shown. Commas, decimals and negatives are accepted.

Examples

Conversion	Result
1 in	2.54 cm
84 m²	about 25.41 pyeong
30 pyeong	about 99.17 m²
1 lb	0.45359237 kg
100 °C	212 °F
100 km/h	about 62.137 mph
1 GiB	1,073,741,824 bytes

FAQ

How many centimeters are in an inch?

Exactly 2.54. The inch has been defined as 2.54 centimeters since 1959, so 1 foot is exactly 30.48 cm and 1 mile is exactly 1,609.344 meters. This tool uses those exact values.

What is a pyeong?

It is a traditional Korean unit of floor area used in real estate. One pyeong is 400/121 square meters, about 3.305785 m², or roughly 35.58 square feet. An 84 m² apartment is about 25.4 pyeong.

What is the difference between KB and KiB?

KB, MB and GB step by 1,000 (decimal, SI), while KiB, MiB and GiB step by 1,024 (binary). Drive makers use decimal sizes and some operating systems display binary sizes with decimal labels, which is why capacities look different.

How do I convert Fahrenheit to Celsius?

Subtract 32 and multiply by 5/9. So 98.6 °F is 37 °C. Kelvin is Celsius plus 273.15. Temperature scales have different zero points, so it is not a simple multiplication.