How unit conversion works
Every conversion uses a fixed relationship between units. To convert from one unit to another, the tool first changes your value into a common base unit (such as metres or kilograms) and then into the unit you want. Temperature is handled separately, because Celsius, Fahrenheit and Kelvin do not simply scale by a single number.
Handy conversions to remember
- 1 inch = 2.54 centimetres
- 1 mile = 1.609 kilometres
- 1 kilogram = 2.205 pounds
- 1 US cup = about 237 millilitres
- 1 US tablespoon = about 14.8 millilitres, 1 teaspoon = about 4.9 millilitres
Temperature formulas
- Fahrenheit to Celsius: (°F − 32) × 5 ÷ 9
- Celsius to Fahrenheit: °C × 9 ÷ 5 + 32
- Celsius to Kelvin: °C + 273.15
Cooking measures: a warning
Cup and spoon sizes differ between countries. This tool uses US customary measures. A UK or metric cup is often 250 ml and a metric tablespoon is 15 ml. For baking, weighing ingredients in grams is more accurate than measuring by volume.
Why a result may look rounded
Results show up to eight decimal places and are rounded to ten significant digits to avoid long strings of floating-point noise.
Frequently asked questions
Are these US or imperial gallons?
US gallons. A UK (imperial) gallon is about 20% larger.
How accurate is it?
It uses the exact international definitions for each unit, so results are accurate to many decimal places.