How to use
- Choose a category, enter a value, and pick the units to convert from and to. The result updates as you type.
- Use the ⇄ button to swap the two units.
- The table below the result shows the same value in every unit of the category.
- You can enter negative numbers and decimals, using either a period or a comma as the decimal point (2.5 or 2,5).
How conversions work
Each category has a base unit, such as the meter for length and the kilogram for weight. A value is converted to the base unit and then to the target unit, using exact defined factors: 1 inch is exactly 0.0254 m, so inches to centimeters is a multiplication by 2.54.
Temperature uses formulas instead of a single factor: °F = °C × 9/5 + 32 and K = °C + 273.15. Results show up to 12 significant digits.
Worked examples
- Height: 5 ft 10 in is 70 inches. Choose Length, enter 70, and convert Inch to Centimeter: 70 × 2.54 = 177.8 cm.
- Body weight: 150 lb × 0.45359237 = 68.0388555 kg.
- Fever: 100 °F is (100 − 32) × 5/9 = 37.7777777778 °C, or about 37.8 °C.
- Marathon: 42.195 km is 26.2187574565 miles.
- Speed limit: 100 km/h is 62.1371192237 mph.
- Storage: a 500 GB drive holds 500,000,000,000 bytes, which is 465.661287308 GiB, the figure many operating systems show.
Common conversions
- 1 inch = 2.54 cm, 1 foot = 12 inches = 30.48 cm
- 1 meter = 3.28083989501 feet
- 1 mile = 5280 feet = 1.609344 km, 1 km = 0.621371192237 miles
- 1 nautical mile = 1852 m, 1 knot = 1.852 km/h
- 1 pound = 0.45359237 kg, 1 kg = 2.20462262185 pounds
- 1 ounce = 28.349523125 g
- 1 US gallon = 3.785411784 L, 1 imperial gallon = 4.54609 L
- 1 US cup = 8 US fluid ounces
- 1 acre = 4046.8564224 m², 1 hectare = 2.47105381467 acres
- 0 °C = 32 °F = 273.15 K, −40 °C = −40 °F
- 1 GB = 1000 MB, 1 GiB = 1024 MiB
Standards used
- The inch, foot, yard, mile, ounce and pound use the international definitions of 1959: 1 yard = 0.9144 m and 1 pound = 0.45359237 kg.
- US liquid measures (fluid ounce, cup, pint, quart, gallon) follow US customary units, where 1 US gallon = 3.785411784 L. The imperial gallon used in the UK is 4.54609 L.
- Data units: KB, MB, GB and TB are decimal SI prefixes (powers of 1000), while KiB, MiB, GiB and TiB are binary IEC prefixes (powers of 1024). 1 byte = 8 bits.
- Temperatures below absolute zero (−273.15 °C, 0 K) do not exist, so the converter shows a message instead of a result.
Frequently asked questions
How many cm are in an inch?
There are exactly 2.54 centimeters in an inch. A foot is 12 inches, or 30.48 centimeters.
How many feet are in a meter?
One meter is about 3.28083989501 feet, or roughly 3 feet 3.37 inches.
How many pounds are in a kilogram?
One kilogram is about 2.20462262185 pounds. In the other direction, 1 pound is exactly 0.45359237 kilograms.
How do I convert km to miles?
Multiply kilometers by about 0.621371, or divide by 1.609344, since 1 mile is exactly 1.609344 km. For example, 100 km is 62.1371192237 miles.
What is the formula for Celsius to Fahrenheit?
°F = °C × 9/5 + 32, so 25 °C is 77 °F. To go back, use °C = (°F − 32) × 5/9.
What is the difference between a US gallon and an imperial gallon?
A US gallon is 3.785411784 liters and an imperial (UK) gallon is 4.54609 liters, so an imperial gallon is about 1.2 US gallons.
What is the difference between GB and GiB?
GB uses powers of 1000 (1 GB = 1,000,000,000 bytes) and GiB uses powers of 1024 (1 GiB = 1,073,741,824 bytes). Storage makers usually use GB, while many operating systems report GiB.