Live unit converter
Unit converter
Enter a value, choose its unit and read the same quantity in every other unit in its family. Each result comes from the exact definitions listed beside it.
The live converter needs JavaScript. The reference values under each family work without it, and they state the exact definitions the converter uses.
Results are shown to six significant figures. The arithmetic keeps full precision until the display, so a rounded figure never feeds the next step.
Mass
Mass is the amount of matter in an object, and it is the quantity most goods are weighed by. The kilogram is the SI base unit of mass, and every figure in this family passes through grams, one thousandth of a kilogram.
Reference values
- Gram (g)
- One thousandth of a kilogram, used for small quantities of goods and ingredients.
- Kilogram (kg)
- 1,000 grams exactly. The usual metric unit for bulk goods and ingredients.
- Metric tonne (t)
- 1,000 kilograms, which is 1,000,000 grams exactly.
- Avoirdupois ounce (oz)
- 28.349523125 grams exactly. One sixteenth of a pound.
- Pound (lb)
- 0.45359237 kilograms exactly, or 16 avoirdupois ounces.
- Stone (st)
- 14 pounds, which is 6.35029318 kilograms exactly.
- Troy ounce (oz t)
- 31.1034768 grams exactly. Traditionally used for precious metals.
Mass conversions are simple factors. Multiply the value by the factor of its unit to reach grams, then divide by the factor of the unit you want.
Length
Length is the distance between two points. The metre is the SI base unit, and the imperial units below are defined exactly in terms of it, so every conversion in this family is a fixed factor.
Reference values
- Millimetre (mm)
- One thousandth of a metre.
- Centimetre (cm)
- 0.01 metres exactly.
- Metre (m)
- The SI base unit of length.
- Kilometre (km)
- 1,000 metres exactly.
- Inch (in)
- 25.4 millimetres exactly.
- Foot (ft)
- 12 inches, or 0.3048 metres exactly.
- Yard (yd)
- 3 feet, or 0.9144 metres exactly.
- Mile (mi)
- 1,760 yards, or 1,609.344 metres exactly.
Length conversions use the same pattern as mass: multiply by the factor of the starting unit to reach metres, then divide by the factor of the target unit.
Volume
Volume is the space a liquid or a bulk material occupies. Recipes and makers use several volume units, and the fluid ounce and the gallon differ between American and imperial systems, so the names alone are not enough to convert them.
Reference values
- Millilitre (mL)
- One cubic centimetre, exactly.
- Litre (L)
- 1,000 millilitres exactly, which is one cubic decimetre.
- US fluid ounce (US fl oz)
- 29.5735295625 millilitres exactly. One 128th of a US gallon.
- US cup (US cup)
- 8 US fluid ounces, or 236.5882365 millilitres exactly.
- Imperial fluid ounce (imp fl oz)
- 28.4130625 millilitres exactly. One 160th of an imperial gallon.
- US gallon (US gal)
- 3.785411784 litres exactly.
- Imperial gallon (imp gal)
- 4.54609 litres exactly.
Volume is a different quantity from mass. To move between the two, a density is needed; the field guide explains that step.
Temperature
Temperature scales differ in both their zero points and their degree sizes, so converting between them takes a formula rather than a simple factor. The converter moves each value through kelvin, which starts at absolute zero.
Reference values
- Degree Celsius (°C)
- Water freezes at 0 °C and boils at 100 °C at standard atmospheric pressure.
- Degree Fahrenheit (°F)
- Water freezes at 32 °F. A Fahrenheit degree is smaller than a Celsius degree, so the scales need a formula.
- Kelvin (K)
- Starts at absolute zero. Its degree is the same size as a Celsius degree.
K = °C + 273.15 (exact)
°F = °C × 9 ÷ 5 + 32