Physics Unit Converter

The Physics Unit Converter covers three families of units that come up constantly in engineering, science and everyday technical work: speed (m/s, km/h, mph, knot), pressure (Pa, kPa, bar, psi, atm) and energy (J, kJ, cal, kcal, Wh, kWh).

Pick a category, enter a value, and convert between any two units within it.

These conversions are easy to get wrong from memory.

A knot is a nautical mile per hour, not quite the same as a regular mph; one atmosphere is 14.7 psi, not a round number; and energy units quietly mix the worlds of food (kilocalories), electricity (kilowatt-hours) and pure SI (joules), where a single kWh is a hefty 3.6 million joules.

This tool routes each conversion through the SI base unit for that category — metres per second, pascals, joules — so the factors are applied consistently and the result is accurate to full floating-point precision.

As with the general unit converter, it refuses to convert across categories, so you can never accidentally turn a pressure into an energy.

Whether you are reading a tyre pressure off a foreign manual, comparing the energy in a battery to a meal, or converting a wind speed between knots and km/h, you get a dependable answer instantly.

The maths runs entirely in your browser with nothing uploaded, and it works offline.