About kwcalculator.com

kwcalculator.com converts between kilowatts, amps, volts, horsepower, kilowatt-hours, BTU/hr, kVA, watts, and tons of refrigeration, for DC, single-phase AC, and three-phase AC circuits. Every result shows the formula behind it, so you can check the math yourself instead of trusting a black box.

We built it because most calculators we found online either skipped power factor entirely, used rounded or outdated conversion constants, or buried a simple conversion behind autoplay video ads and multi-step forms. This site runs every calculation live in your browser as you type, with no submit button and no account required.

Who uses it

Electricians sizing breakers and conductors, engineers converting between metric and imperial power units, HVAC technicians matching tonnage to BTU/hr, facility managers sizing backup generators, and homeowners trying to work out what size generator or EV charger circuit they need. The calculators are built to answer a specific, practical question quickly, not to be a general-purpose scientific calculator.

How the formulas are sourced and checked

Every constant on this site (0.7457 kW per mechanical horsepower, 3,412.14 BTU/hr per kW, 3.51685 kW per ton of refrigeration, and so on) is sourced from IEEE, NIST, and NEC reference values, not rounded approximations. The conversion logic lives in a single shared module used by every calculator on the site, so a fix or an update applies everywhere at once instead of drifting between pages.

What we do not do

No account, no paywall, no popup asking you to subscribe before you see a result. We do not sell or share the numbers you type into a calculator, because they never leave your browser in the first place, only the final result is ever shown, and it is computed locally on your device. See the privacy policy for the full detail on what limited, aggregated analytics we do collect.