Horsepower Calculator
Convert between horsepower, torque, and engine RPM using the standard automotive power formula.
Reviewed by the CalcCafe editorial team · Last updated 1 July 2026 · How we test our tools
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.
How fast is 4,000 horsepower?
Horsepower measures power, not speed, so 4,000 hp does not translate to a single mph figure; 4,000 hp equals 4,000 x 0.7457 = 2,983 kW. How fast a 4,000 hp vehicle goes depends on its weight, gearing, tires and aerodynamics: in a lightweight drag car it means quarter-mile runs in a few seconds, while the same power in a heavy truck or boat produces far lower speeds. Top speed rises with roughly the cube root of power, so doubling horsepower only raises top speed by about 26%.
How is 1 hp calculated?
One horsepower is defined as 33,000 foot-pounds of work per minute, which is 550 foot-pounds per second, or 745.7 watts. James Watt set that figure in the 1700s to describe how much work a draft horse could do lifting a load. The 5252 in the formula HP = torque x RPM / 5252 comes from dividing 33,000 by 2 pi, which converts rotational torque and speed into that same unit of work per minute.
How much is 80 horsepower?
80 hp is 80 x 0.7457 = 59.7 kW, roughly the output of a small economy car, a compact tractor or a mid-size outboard motor. At 3,000 RPM an 80 hp engine is producing 80 x 5252 / 3,000 = 140 lb-ft of torque, and at 6,000 RPM only 70 lb-ft for the same power. Enter 80 in the Find Torque mode with your RPM to see the figure for your engine.
Is 1 hp equal to a horse?
Not exactly; 1 hp was James Watt's estimate of the sustained work rate of a draft horse, 33,000 foot-pounds per minute. A real horse can produce several times that in a short burst, with peak outputs around 10 to 15 hp measured in studies, but it cannot sustain that all day. The unit stuck as a marketing comparison for steam engines and has been the standard automotive power unit ever since.
What is 400 WHP to hp?
400 wheel horsepower (WHP) is roughly 445 to 500 crank horsepower, depending on drivetrain loss. Power is lost through the transmission, driveshaft and differential, typically about 10 to 15% for manual and rear-wheel-drive cars and 15 to 20% for automatics and all-wheel drive, so 400 / 0.85 = 471 hp at 15% loss and 400 / 0.80 = 500 hp at 20%. Manufacturers quote crank horsepower, which is why dyno numbers always read lower than the spec sheet.
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Sources & references
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