Horse Power
Estimate engine or machine power from multiple methods. Free online calculator with formulas and step-by-step solutions.
Key formula
HP = 550 ft-lb/s and related power formulas
How do you calculate horsepower?
Find power in watts first (P = W/t or P = Fv), then convert: hp ≈ P_watts / 746. Or multiply horsepower by 746 to get watts. Horsepower is not a force; it is a rate of doing work.
About this tool
Horsepower is a power unit — how fast work is done — often used for engines and motors. This page connects hp to watts so you can convert or estimate mechanical power without mixing definitions.
How to use this calculator
- Choose the variable you want to solve for and confirm which values are already known.
- Enter inputs in consistent units before calculating so the formula is applied correctly.
- Check whether the result is physically reasonable by comparing it with the size of the inputs.
- Use the step-by-step breakdown to see how the equation was rearranged and evaluated.
Worked examples
Example 1: watts to hp
P = 1492 W. hp = 1492 / 746 ≈ 2.0 hp.
Example 2: hp to watts
Rated 10 hp. P ≈ 10 × 746 = 7460 W.
Example 3: from work and time
W = 22 380 J in t = 10 s. P = W/t = 2238 W ≈ 3.0 hp.
Frequently asked questions
How many watts in one horsepower?
About 746 W for mechanical horsepower in most school and engineering conversions. Always check if your problem uses a different definition.
Is horsepower the same as torque?
No. Torque is a turning effect (N·m). Horsepower is power (rate of work). Engines are often rated in both, but they are different quantities.
Should I use P = W/t or P = Fv?
Use whichever knowns you have. Both give watts; then divide by 746 for mechanical hp.
How does this relate to the power calculator?
The power calculator works in watts with P = W/t. Convert to or from hp here when the question asks for horsepower.
Can I convert metric horsepower the same way?
Metric horsepower is about 735.5 W — close but not identical to 746 W. Use the constant your course specifies.