Unit Converter

Convert a value from one unit to another — length, mass, temperature, pressure, energy and more. Type any unit or combination of units, such as km/h, kWh, N·m or J/(kg·K), and see the value in every common unit at once.

UnitsConversionSI

Inputs

Input examples

Pick a quantity, then choose both units from their lists (click the field or the arrow). You can also type in the unit fields: a symbol (km, kWh, °F) or a name (miles, light year); the quantity follows what you type. Combine units with ·, *, a space or /, and write powers as m², m^2 or m2. Everything after a / is in the denominator: J/kg·K means J/(kg·K). Every SI unit takes a prefix (k, M, m, µ …).

Quantity

From unit

To unit

Value

What is a Unit Conversion?

A measurement is always a number times a unit. 60 seconds and 1 minute are the same length of time: only the unit, and therefore the number, is different. A bigger unit needs a smaller number.

Converting means multiplying by a fraction that is exactly 1, because its top and bottom are equal: . So : the seconds cancel and minutes are left.

Every unit here is defined by its size in SI units, so any two units of the same quantity can be converted. Units of different quantities, such as a force (N) and a mass (kg), cannot: they measure different things. Temperature is the one exception to plain multiplying, because °C and °F do not start at zero kelvin.

1 inch= 2.54 cm exactly

1 lb= 0.45359237 kg exactly

°F= °C × 1.8 + 32

1 kWh= 3.6 MJ

Result

Enter a value and two units above

In Other Units

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SI Prefixes

work on every SI unit

Prefix	Symbol	Factor	Example
tera	T	10¹²	TW, TB
giga	G	10⁹	GPa, GHz
mega	M	10⁶	MJ, MW
kilo	k	10³	km, kN, kWh
hecto	h	10²	hPa
centi	c	10⁻²	cm, cP
milli	m	10⁻³	mm, mL, mA
micro	µ (or u)	10⁻⁶	µm, µF
nano	n	10⁻⁹	nm, ns
pico	p	10⁻¹²	pF

Also: quetta Q (10³⁰), ronna R, yotta Y, zetta Z, exa E, peta P, deca da, deci d, femto f, atto a, zepto z, yocto y, ronto r and quecto q (10⁻³⁰).

Worked Techniques

Multiply by Factors of One

Each fraction is exactly 1, so the speed does not change. Units that appear above and below the line cancel, leaving the unit you want.

Example: km cancels against km, h against h.

Squared and Cubed Units

The factor is raised to the same power as the unit. A common mistake is to use 100 for square metres to square centimetres.

Example:

Temperature Scales

A temperature reading needs an offset. A temperature difference does not: a rise of 1 °C is a rise of 1 K, and 1.8 °F.

Example: body temperature 37 °C = 98.6 °F = 310.15 K.

Sources & Verification

References

BIPM, The International System of Units (SI Brochure), 9th ed., 2019 — Tables 4, 7 and 8 (derived units, prefixes, non-SI units).
A. Thompson & B. N. Taylor, Guide for the Use of the International System of Units (SI), NIST Special Publication 811, 2008 — Appendix B (conversion factors).
IAU Resolutions B2 (2012) and B2 (2015) — astronomical unit and parsec.
CODATA 2022 Recommended Values of the Fundamental Physical Constants, NIST — dalton (atomic mass constant).