Convert units instantly
Choose a category, type a value, and pick the units to convert from and to. The result updates as you type. The converter covers the conversions people search for most: length (meters, kilometers, miles, feet, inches), weight (kilograms, grams, pounds, ounces, stone), volume (liters, milliliters, US gallons, quarts, cups, fluid ounces), area (square meters, square feet, acres, hectares), speed (km/h, mph, m/s, knots) and temperature (Celsius, Fahrenheit, Kelvin).
How the conversions work
Each unit is stored with an exact factor relative to a base unit: meters for length, kilograms for mass, liters for volume, and so on. To convert, the value is multiplied by the "from" factor and divided by the "to" factor. The factors use official definitions: one inch is exactly 2.54 cm, one pound is exactly 0.45359237 kg, and one US gallon is exactly 3.785411784 liters.
Temperature is different because the scales have different zero points, so it uses formulas instead of a single factor:
- °F = °C × 9/5 + 32
- °C = (°F − 32) × 5/9
- K = °C + 273.15
Handy conversions to remember
- 1 mile ≈ 1.609 km; 1 km ≈ 0.621 miles
- 1 kg ≈ 2.205 lb
- 1 foot = 12 inches = 30.48 cm
- 1 US cup ≈ 237 mL; 1 liter ≈ 4.23 US cups
- 1 acre ≈ 43,560 ft² ≈ 0.405 hectares
- Body temperature 37 °C = 98.6 °F; water boils at 100 °C = 212 °F
US vs. UK (imperial) units
US and UK gallons, pints and fluid ounces are different sizes. A UK (imperial) gallon is about 4.546 liters, roughly 20% larger than a US gallon. This converter uses US customary volume units, which are labeled as such.
Frequently asked questions
How many centimeters are in an inch?
Exactly 2.54 centimeters.
How do I convert Celsius to Fahrenheit?
Multiply by 9/5 and add 32. For example, 20 °C = 68 °F.
Are gallons US or UK?
This converter uses US gallons (3.785 L). A UK gallon is 4.546 L.