Horsepower Calculator

What this calculator does

The Horsepower Calculator has two purposes. The definition mode computes power from a force applied over a distance in a given time. The converter mode changes a value between watts, kilowatts, mechanical horsepower, metric horsepower, electrical horsepower, boiler horsepower, and BTU per hour.

Horsepower is a unit of power, which is the rate at which work is done. One mechanical horsepower is 550 foot-pounds per second, or about 745.7 watts. Other horsepower definitions use slightly different conversion factors, so the calculator reports every common definition side by side.

How to use this calculator

1. Choose "From force, distance, and time" or "Convert power units".
2. In definition mode, enter the force, choose its unit, enter the distance and its unit, then enter the time and its unit.
3. In converter mode, enter the amount, choose the source unit, and choose the target unit.
4. Click Calculate.

The definition mode accepts newtons, kilonewtons, pound-force, and kilogram-force; meters, kilometers, miles, and yards; and seconds, minutes, hours, or days. The converter accepts the seven power units listed above.

Formula

Power (watts) = force (newtons) x distance (meters) / time (seconds)
Mechanical horsepower = watts / 745.6998716
Metric horsepower = watts / 735.49875
Electrical horsepower = watts / 746
Boiler horsepower = watts / 9,809.5
BTU per hour = watts / 0.2930710702

To convert between power units, the calculator changes the input to watts first, then divides by the target unit's watt factor. This avoids cumulative rounding between the source and target units.

Default example

The default definition uses 10 newtons, 3 meters, and 2 seconds. The power is 15 watts. That equals about 0.020115 mechanical horsepower, 0.020394 metric horsepower, 0.020107 electrical horsepower, and 0.001529 boiler horsepower.

The default converter changes 1 mechanical horsepower to watts and returns 745.6999 W. It also shows the same power in kilowatts and every other supported horsepower definition.

Assumptions and limitations

• The definition mode assumes a constant force applied along the direction of motion for the full distance and time.
• Real machines have friction, acceleration, and changing loads, so a simple force-distance-time calculation is an idealization.
• Mechanical horsepower is the most common definition for vehicle engines in the United States. Metric horsepower is common in some other markets.
• Boiler horsepower is a historical rating for steam boilers, not a direct measure of an engine's output.
• Conversion factors are standard constants; the displayed values are rounded.

Frequently asked questions

What is the difference between mechanical and metric horsepower?

Mechanical horsepower is defined as 550 foot-pounds per second, or 745.6999 watts. Metric horsepower is defined as 75 kilogram-force meters per second, or 735.49875 watts. The metric unit is about 1.4 percent smaller, so the same power output produces a larger metric horsepower number.

Can I enter pound-force and yards?

Yes. Choose pound-force for the force and yard for the distance. The calculator converts both to SI units before computing power, then reports the result in watts and every horsepower definition.

What is boiler horsepower used for?

Boiler horsepower historically describes a boiler's capacity to evaporate water, roughly 34.5 pounds of water per hour at 212 degrees Fahrenheit. It equals about 9,809.5 watts. It is not a typical unit for car or aircraft engines.

Reference table

Force unit conversions

Amount conversion examples

Power equals force times distance divided by time. Use consistent units before calculating.

Source

Reference: Calculator.net - Horsepower Calculator. Conversion factors follow the standard definitions of mechanical, metric, electrical, and boiler horsepower.