How to use the unit converter
Choose the type of measurement, enter a value and pick the units to convert from and to. The result updates as you type, and a table shows the same value in every unit of that type. Use Swap units to convert the other way.
Exact conversion factors
Since 1959, the inch, foot, yard, mile and pound have been defined exactly in metric units, so these conversions have no rounding at all:
| Unit | Exact value |
|---|---|
| 1 inch | 2.54 cm |
| 1 foot | 0.3048 m (12 inches) |
| 1 yard | 0.9144 m (3 feet) |
| 1 mile | 1.609344 km |
| 1 nautical mile | 1.852 km |
| 1 pound | 0.45359237 kg |
| 1 ounce | 28.349523125 g |
| 1 US gallon | 3.785411784 L |
| 1 UK (imperial) gallon | 4.54609 L |
| 1 acre | 4,046.8564224 m² (43,560 ft²) |
| 1 hectare | 10,000 m² |
Worked examples
25 cm to inches: 25 ÷ 2.54 = 9.842519685 in (to 10 significant figures).
Temperature: °F = °C × 9 ÷ 5 + 32, so 37 °C = 98.6 °F. °C = (°F − 32) × 5 ÷ 9, so 350 °F ≈ 176.67 °C.
US and UK units aren't the same
A US gallon is about 3.79 litres but a UK gallon is 4.55 litres, and US and UK pints and fluid ounces differ too. A US cup is 236.6 mL. Check which system a recipe or fuel figure uses.
Indian land units
A cent is one hundredth of an acre (435.6 ft²), common in South India. A guntha is 1,089 ft² (121 square yards), used in Maharashtra, Gujarat and Karnataka. One square yard is also called a gaj. Units such as the bigha differ from state to state, so they aren't included.
Need volume for a building job? Try the concrete calculator.
Frequently asked questions
How many pounds are in a kilogram?
1 kg = 2.20462262 lb, because 1 lb is exactly 0.45359237 kg.
How do I convert km/h to mph?
Divide by 1.609344. 100 km/h is about 62.14 mph.
Sources
Formulas checked 29 October 2026. How we test our calculators. Conversions use the exact international definitions. Results are rounded to 10 significant figures.