Horsepower ↔ Torque Calculator (5252 Rule)
HP = torque × RPM ÷ 5252 — convert either way at any RPM, with kW, PS and Nm, and the reason every dyno chart crosses at 5252.
Torque is what the engine twists; horsepower is how fast it can keep twisting. Below 5252 RPM torque (in lb-ft) is numerically bigger, above it HP is — which is why every honest dyno overlay crosses exactly there.
Formula
⚠️ Estimates for planning and education — verify against manufacturer data and measured results. Performance figures are not a substitute for safe, legal driving.
HP = torque × RPM ÷ 5252 — convert either way at any RPM, with kW, PS and Nm, and the reason every dyno chart crosses at 5252.
About Horsepower ↔ Torque Calculator (5252 Rule)
Horsepower was invented by James Watt to sell steam engines to people who owned horses, and it's still just torque with a clock attached: HP = torque × RPM ÷ 5252. This calculator converts between torque and power at any engine speed — in lb-ft, Nm, hp, kW and PS — and explains the famous 5252 crossing, the 33,000 foot-pounds-per-minute behind it, and why peak-torque and peak-power numbers describe two different personalities of the same engine.
How to use Horsepower ↔ Torque Calculator (5252 Rule)
- 1Enter — sensible defaults are pre-filled so you see a worked result immediately.
- 2Read the live results: .
- 3Check the "With your numbers" line to see the formula HP = torque (lb-ft) × RPM / 5252; 5252 = 33,000 ft-lb/min ÷ 2π substituted step by step.
- 4Adjust inputs (or flip the unit toggle) until the scenario matches yours, then copy or share the result.
Why use Horsepower ↔ Torque Calculator (5252 Rule)?
- ✓Instant, free and private — every calculation runs in your browser, nothing is uploaded
- ✓Built on the published formula HP = torque (lb-ft) × RPM / 5252; 5252 = 33,000 ft-lb/min ÷ 2π with sources cited on the page
- ✓Torque is what the engine twists; horsepower is how fast it can keep twisting. Below 5252 RPM torque (in lb-ft) is numerically bigger, above it HP is — which is why every honest dyno overlay crosses exactly there.
- ✓Switch units, tweak any input and watch every result update live
Frequently asked questions
Where does 5252 come from?+
Watt defined one horsepower as 33,000 foot-pounds of work per minute. Rotational power is torque × angular speed, and one revolution is 2π radians, so HP = torque × RPM × 2π ÷ 33,000 — and 33,000 ÷ 2π = 5252.1. It's a unit artifact, not physics: in metric, kW = Nm × RPM ÷ 9549, and the dyno-chart crossing happens at 9549 instead. Same engine, different bookkeeping.
Which matters more for acceleration — torque or horsepower?+
At the tires, horsepower — because gearing converts RPM into torque multiplication: a high-revving engine making modest crankshaft torque can deliver enormous wheel torque through shorter gears. What 'torquey' engines really offer is power available at LOW rpm — relaxed, shift-free drivability. Two cars with equal power-to-weight accelerate nearly identically when geared properly, however different their torque peaks look on paper.
Why do hp, PS and kW versions of my car's spec differ?+
Three unit systems and several test codes: 1 hp (SAE) = 745.7 W, 1 PS (metric horsepower) = 735.5 W — so a 300-PS European spec is 296 hp, and both are 220.6 kW. Add measurement differences (SAE J1349 net vs old gross ratings vs DIN) and the same engine can wear four numbers. Convert units first, then compare test codes; this tool handles the units.
Is a dyno's 'horsepower' measured or calculated?+
Calculated — inertia and brake dynos measure torque (from roller acceleration or load-cell reaction) and RPM, then apply this page's formula. That's why torque is the honest primary trace and why smoothing settings change peak-HP bragging numbers. Wheel dynos also read 10–20% below crank ratings: driveline friction, tire deformation and accessory losses live between the crank and the rollers.
Related Field tools
Sunrise & Sunset Calculator
Exact rise, set, solar noon and day length for any place and date — the NOAA solar equations with the refraction fine print included.
● LiveGolden Hour & Blue Hour Calculator
Tonight's golden hour and blue hour, computed from sun elevation — the photographer's light windows with the angles that define them.
● LiveDay Length Calculator
Hours of daylight for any date and latitude, how fast it's changing, and the swing between your solstices.
● Live