Horsepower Calculators
Everything you need to calculate engine, wheel, and theoretical horsepower.
Horsepower is the measure of how much work an engine or motor can do over time. This hub brings together every horsepower calculator on the site — from the core torque-and-RPM formula to wheel, flywheel, boost, and altitude-corrected horsepower — so you can find the exact tool for your engine, vehicle, or build.
What Is Horsepower?
One horsepower equals 33,000 foot-pounds of work per minute, a figure James Watt chose to compare steam engines with the draft horses they replaced. In practical terms, horsepower tells you how quickly an engine can deliver its torque. Two engines can make identical torque, but the one that sustains it to higher RPM produces more horsepower — which is why high-revving engines and big-displacement diesels reach the same power figures by very different routes.
How Horsepower Is Calculated
The foundation of every engine-power calculation is the 5252 relationship:
From this base, different calculators add real-world corrections: wheel horsepower subtracts drivetrain loss, boost horsepower adds the gains from forced induction, and altitude loss accounts for thinner air at elevation. If you already have a power figure and need torque, the HP to torque calculator reverses the math.
Which Horsepower Calculator Should You Use?
| If you want to… | Use this calculator |
|---|---|
| Find HP from a dyno torque & RPM figure | HP from Torque & RPM |
| Estimate engine (crank) horsepower | Engine Horsepower |
| Convert crank HP to power at the wheels | Wheel Horsepower (WHP) |
| Work back from wheel HP to flywheel HP | Flywheel Horsepower |
| See HP added by a turbo or supercharger | Boost Horsepower |
| Correct power for elevation | Altitude Loss |
Gross, Net, Crank and Wheel Horsepower
The same engine can be quoted at several different horsepower numbers depending on where and how it is measured. Gross horsepower is measured on an engine dyno with no accessories. Net (SAE) horsepower includes the alternator, water pump, and exhaust — the figure manufacturers advertise. Crank or flywheel horsepower is power at the engine output, while wheel horsepower (WHP) is what reaches the ground after drivetrain losses of roughly 10% (FWD), 15% (RWD), or 20%+ (AWD). Knowing which number you are looking at prevents confusing comparisons. For the full explanation, read our guide on wheel HP vs crank HP.
Each calculator in this hub uses standard published formulas. Results are estimates that depend on the accuracy of your inputs and do not replace a measured dyno run.
Frequently Asked Questions
Horsepower is a unit of measurement for power, or the rate at which work is done.
If you know torque and RPM, use HP = (torque × RPM) ÷ 5252. It's the most direct method and the basis for most engine power figures.
Crank horsepower is measured at the engine; wheel horsepower is what reaches the ground after drivetrain losses of roughly 10–25% depending on the drivetrain.
Use HP from Torque & RPM for dyno figures, Wheel HP for power at the wheels, Boost HP for forced induction, and Engine HP if you're estimating from a build.
Yes, every calculator is free, needs no sign-up, and runs entirely in your browser so your inputs stay private.