Horsepower Calculator
Convert between horsepower, torque, and engine RPM using the standard automotive power formula.
Example
An engine making 300 lb-ft of torque at 5,000 RPM produces 300 x 5000 / 5252 = 285.6 hp (about 213 kW).
How it works
Mechanical power follows HP = torque (lb-ft) x RPM / 5252, where 5252 comes from 33,000 ft-lb/min per horsepower divided by 2 pi. Rearranged, torque = HP x 5252 / RPM. The two curves always cross at 5252 RPM.
Good to know
This Horsepower Calculator converts between horsepower, torque, and engine speed using the standard automotive equation HP = torque (lb-ft) x RPM / 5252. It runs two ways: enter torque and RPM to find horsepower, or switch to the "Find Torque" mode and enter horsepower and RPM to solve for torque. Each calculation also shows the equivalent power in kilowatts (1 hp = 0.7457 kW), making it handy for car enthusiasts, mechanics, students, and anyone comparing dyno figures across imperial and metric specs.
You'd reach for it when you have a dyno sheet, a manufacturer spec, or a build target and need to fill in the missing variable. For example, if a tuner quotes peak torque at a known engine speed but not peak power, this tool gives you the horsepower figure at that exact RPM, and vice versa. It's also useful for sanity-checking numbers you see in ads or forum posts that may have been rounded or mislabeled.
Read the result as the power or torque at one specific engine speed, not across the whole rev range. Because real engines produce torque that rises and falls with RPM, a single calculation describes one point on the curve. The headline output appears in the large display, while the stat row breaks out torque, horsepower, RPM, and kW together so you can see how they relate at that operating point.
One practical caveat: this formula only works with torque in pound-feet and the constant 5252. If your figures are in newton-metres, convert them first (1 lb-ft is about 1.356 Nm), and remember that the 5252 RPM crossover point is a property of these specific units, not a universal engine characteristic. Treat the output as a clean mathematical estimate; real-world flywheel versus wheel horsepower and drivetrain losses are not part of this calculation.
Frequently asked questions
Why is 5252 used in the horsepower formula?
One horsepower equals 33,000 ft-lb of work per minute. Dividing 33,000 by 2 pi (the radians in one revolution) gives 5252, the constant that links torque in lb-ft and RPM to horsepower.
Why do horsepower and torque always cross at 5252 RPM?
Because HP = torque x RPM / 5252, the two values are numerically equal exactly when RPM is 5252. Below that RPM torque reads higher; above it horsepower reads higher.
Is my data uploaded anywhere?
No — this calculator runs entirely in your browser. Your inputs never leave your device, and it works offline once loaded.
Is this calculator free?
Yes, completely free with no sign-up and no limits.
People also ask
How do you calculate horsepower from torque and RPM?
Multiply torque in pound-feet by engine RPM, then divide by 5252. For example, 300 lb-ft at 5,000 RPM gives 300 x 5000 / 5252 = about 285.6 hp.
How do I convert horsepower to kilowatts?
Multiply horsepower by 0.7457 to get kilowatts. So 285 hp is roughly 213 kW, and to go back from kW to hp you divide by 0.7457.
Is wheel horsepower the same as engine horsepower?
No. Engine (crank or flywheel) horsepower is measured at the engine, while wheel horsepower is measured at the drive wheels and is lower because of drivetrain losses through the transmission, driveline, and tires. This calculator computes a raw figure from the formula and does not account for those losses.
What is the difference between horsepower and torque?
Torque is the rotational force an engine produces, while horsepower is the rate at which that work is done over time. Horsepower factors in engine speed, which is why the same torque produces more horsepower at higher RPM.
How do I convert pound-feet to newton-metres?
Multiply pound-feet by about 1.356 to get newton-metres, and divide by 1.356 to convert back. This calculator expects torque in pound-feet, so convert metric figures before entering them.
Can I find torque if I only know horsepower and RPM?
Yes. Rearranging the formula gives torque = horsepower x 5252 / RPM. Switch the tool to its Find Torque mode, enter horsepower and RPM, and it returns torque in pound-feet.
Why does peak horsepower happen at a higher RPM than peak torque?
Because horsepower scales with both torque and engine speed, power keeps climbing as RPM rises even after torque has started to fall, so peak horsepower typically occurs at a higher RPM than peak torque.
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