Covers energy, pressure, force, power, magnetic field, frequency and electric charge. For length, weight, volume, temperature, area or speed, use the Unit Converter instead.
The physics units that a general converter usually skips
Length, weight, volume, temperature, area and speed are covered by the general Unit Converter. This tool picks up where that one stops: energy, pressure, force, power, magnetic field, frequency and electric charge, the units that turn up in an A-level physics paper, an engine spec sheet, or a tyre pressure label rather than in everyday shopping and cooking.
Two figures that get mixed up constantly
| Mix-up | Why it matters |
|---|---|
| Mechanical/UK horsepower (hp) vs metric horsepower (CV) | 1 hp = 745.7 W, 1 CV = 735.49875 W: a European car spec sheet quoted in CV understates the figure you would get quoting the same engine in hp |
| Bar vs psi | UK and European tyre gauges are usually marked in both, but a reading taken from a US pump in psi needs converting before it means anything against a bar-based recommended pressure |
| mmHg vs Torr | Close but not identical: 1 Torr is defined as 1/760 atm (133.3224 Pa), 1 mmHg is a separate conventional unit that only matches Torr to four decimal places |
What this tool does not do
This is a straight linear conversion between units of the same physical quantity: it does not convert between different quantities (energy to power needs a time value, force to pressure needs an area), and it does not handle length, weight, volume, temperature, area or speed. For those, go to the Unit Converter. For the constants used in some of these conversions, such as standard gravity, see the Scientific Constants Reference.
Reading the result
Pick a category first, since the From and To lists only show units that share the same physical quantity: swapping between energy and pressure units directly is not physically meaningful, which is why the two lists always stay in step with the category selected above. The line under the result restates the reference conversion for the pair you have chosen, so you can check the factor itself rather than just trusting the output.