QuickCalculators computes mechanical power from force, distance, and time, then converts among mechanical horsepower, metric horsepower, electrical horsepower, boiler horsepower, watts, and related units. Enter the work-rate inputs or a known power value; read the equivalent figures with each horsepower definition labeled.
Calculate power from force, distance and time
Power is work per unit time. When a constant force moves through a distance in a measured time, power equals force times distance divided by time. Horsepower Calculator evaluates that quotient and can express it in watts or in a selected horsepower unit.
James Watt's historical marketing of steam engines popularized the horsepower name; the SI unit of power remains the watt.
Example: a force of 500 newtons through 20 metres in 5 seconds yields work of 10,000 joules and power of 2,000 W. Converting that wattage into mechanical horsepower uses the factor for the chosen definition. Without a definition tag, a bare "horsepower" label stays ambiguous.
Convert between power units
Conversion multiplies or divides by fixed factors among watts, kilowatts, BTU per hour, and the several horsepower definitions. QuickCalculators applies NIST-style constants for those links so a value entered in one unit appears in the others. Changing the output unit converts the number rather than relabeling it in place without scaling.
One mechanical horsepower is 745.7 W. One metric horsepower is 735.5 W. Electrical horsepower is 746 W. Boiler horsepower is much larger at about 9,809.5 W. Those gaps matter when comparing nameplates across regions and eras.
Avoid this common mistake
"Horsepower" names four different units that can differ by up to about thirteen times when boiler horsepower is in the mix. A figure without its definition is ambiguous. Mechanical, metric, electrical, and boiler horsepower are not interchangeable labels for one size.
Reading "100 hp" on a chart without knowing which definition applies can misstate power by a large factor. The calculator always names the definition beside the number so the unit is not left implicit.
Read the horsepower definitions table
| Name | Approx. watts |
|---|---|
| Mechanical hp | 745.7 W |
| Metric hp | 735.5 W |
| Electrical hp | 746 W |
| Boiler hp | 9,809.5 W |
BTU per hour also appears in heating contexts; converting through watts keeps the path consistent. Engine brake horsepower ratings on vehicles use test procedures beyond the simple force-distance-time model on this page. The mechanical calculation here is the physics definition of power, not a dynamometer protocol.
Frequently asked questions
How do you calculate horsepower?
To calculate horsepower from force, distance, and time, compute power as force times distance over time in watts, then divide by the watt equivalent of the chosen horsepower definition. The calculator performs that conversion after the wattage is known.
What is one horsepower in watts?
One mechanical horsepower is 745.7 watts, one metric horsepower is 735.5 watts, one electrical horsepower is 746 watts, and one boiler horsepower is about 9,809.5 watts. Always name which horsepower is meant. The table on this page lists those values together.
What is the difference between mechanical and metric horsepower?
Mechanical horsepower is 745.7 W and metric horsepower is 735.5 W, a difference of a little over one percent. They are close but not identical. Mixing them without conversion introduces a small systematic error.
Why is horsepower not an SI unit?
Horsepower is not an SI unit because the SI unit of power is the watt. Horsepower survives as a customary and historical unit in engines and heating. Conversions to watts keep calculations aligned with SI.
What is a BTU?
A BTU is a British thermal unit, a measure of energy. BTU per hour is a power unit used in heating and cooling. Converting BTU per hour through watts links that measure to horsepower and kilowatts on this page.
How is engine horsepower different from this calculation?
Engine horsepower ratings often come from standardized dynamometer tests and correction factors, not from a single classroom force-distance-time trial. This calculator evaluates the physics power formula and unit conversions. Vehicle nameplate methods can differ in procedure even when the unit name matches.
Summary
Horsepower Calculator turns force, distance, and time into power and converts among mechanical, metric, electrical, and boiler horsepower plus watts. Mechanical horsepower is 745.7 W while boiler horsepower is about 9,809.5 W, so unlabeled "hp" is ambiguous. The watt remains the SI power unit. Engine ratings may use test protocols beyond the simple work-rate model shown here.