Convert between watts, horsepower, BTU/hr, kilowatts, and foot-pounds per second.
Enter a power value in any of five units - watts, kilowatts, horsepower, BTU per hour, or foot-pounds per second - and the tool returns the equivalent in the other four. Every figure follows from a fixed definition, so the conversion is exact no matter what produced the power: a motor, a heater, or a lamp. The thing people most often get wrong is scale. One horsepower is 0.746 kW, not 1 kW, and a nameplate horsepower figure is shaft output, not the electrical draw at the wall. The tool converts rates only; it will not turn kilowatt-hours into watts.
A concrete input and expected output from the current implementation.
Input
1 hp
Expected output
745.7 W, 0.7457 kW, 2544.43 BTU/hr, 550 ft-lbf/s
Mechanical horsepower is defined as 550 ft-lbf/s, so that figure is exact by definition. Multiplying 550 by 1.3558 W per ft-lbf/s gives 745.7 W, and dividing 745.7 W by 0.293071 W per BTU/hr gives 2544.43 BTU/hr.
All five units are defined against the watt, which is one joule per second. Mechanical horsepower is exactly 550 foot-pounds per second, which works out to 745.7 watts. One BTU per hour is a 1055.056-joule BTU spread across 3600 seconds, or 0.293071 watt. The tool applies these constant ratios to your input; no factor changes with the device, fuel, or conditions.
You enter one value and the unit it is measured in; the tool derives the other four from the fixed ratios. Because every ratio is an exact constant rather than a rounded approximation, converting a result back to the starting unit reproduces the original value. Fractions and decimals such as 0.75 hp behave the same as whole numbers.
They come from different definitions and are not close. Mechanical horsepower is defined as 550 ft-lbf/s, which is 745.7 W. The intuition that they are similar comes from metric horsepower at 735.5 W, which is still not 1 kW. Only 1000 W is a kilowatt, and no horsepower variant reaches it.
No, not directly. The bill measures energy, while this tool converts power, which is a rate. A kilowatt-hour is already power multiplied by time: a device drawing 2 kW for three hours uses 6 kWh. To sanity-check a bill, multiply each appliance's kW rating by its hours of use and sum.
The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.
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