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Unit Converter

Instantly convert between units of length, mass, temperature, energy, speed, area and volume.

The unit converter lets you instantly transform values between the most widely used measurement systems: the International System (SI), the imperial system and other commonly used units. The categories covered are length, mass, temperature, energy, speed, area and volume, covering the most frequent conversions in science, engineering and everyday life.

For each category, select the source unit and target unit, enter the value and you will get the result instantly. A quick reference table is also shown with equivalent values for 1, 10, 100 and 1,000 units. The converter uses standardised conversion factors or scientific consensus values.

Quick conversion table

1

0,001

10

0,01

100

0,1

1000

1

About this converter

This converter performs instant conversions between the most common units of the International System (SI) and other measurement systems. Conversions use exact factors where standardised (e.g. 1 inch = exactly 0.0254 m) or scientific consensus values otherwise.

How conversions work

Converting units means multiplying the original value by a factor that relates both units to a common reference. Internally, the converter first transforms the value into that category's International System base unit (metres for length, kilograms for mass, joules for energy) and then converts it to the target unit. This two-step method ensures that all conversions within the same category are consistent with one another and avoids accumulating rounding errors.

Most common conversions

UnitEquals
1 inch2.54 cm
1 foot30.48 cm
1 mile1.609 km
1 pound0.454 kg
1 ounce28.35 g
1 US gallon3.785 L
0 °C32 °F
100 °C212 °F
1 kcal4.184 kJ

Frequently asked questions

Because the zero point of °C and °F is arbitrary (it does not correspond to the absence of heat). Kelvin has the absolute zero. That is why the conversion requires adding or subtracting constants in addition to the multiplicative factor.

The International System of Units (SI). Its base units are: metre (m), kilogram (kg), second (s), ampere (A), kelvin (K), mole (mol) and candela (cd).

One US gallon is approximately 3.785 litres. The imperial gallon (used in the United Kingdom) is 4.546 litres. This calculator uses the US gallon.

One statute mile is exactly 1,609.344 metres, i.e. approximately 1.609 km. The nautical mile is 1.852 km and is used in aviation and sailing.

In everyday language they are used as synonyms, but in physics they are different things. Mass is the amount of matter in an object and is measured in kilograms; it is the same on Earth, on the Moon or in space. Weight is the force with which gravity pulls on that mass and is measured in newtons; it changes with the local gravity. This converter works with mass (kg, g, lb, oz), which is what you usually need in everyday life, cooking or commerce.

Not directly, because they measure different physical quantities: it makes no sense to convert litres to kilometres. Some quantities are related by a density or a specific factor (one litre of pure water weighs about 1 kg at 4 °C), but that equivalence depends on the substance and is not a pure unit conversion. That is why the converter is organised by categories and only lets you convert between units that measure the same quantity.

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