Horsepower and Torque Calculator
Converts torque to power or power to torque at a given engine speed, in kW, hp, Nm and lb·ft.
Share sends a link that reopens these numbers. Copy details pastes the full breakdown as a list.
The formula
kW = Nm × rpm ÷ 9,549 hp = lb·ft × rpm ÷ 5,252
Both constants are 60 ÷ 2π scaled for the units — power is torque times angular velocity. The 5,252 in the imperial version is why horsepower and torque in lb·ft cross at exactly that rpm on every dyno plot.
What to watch out for
What the two numbers mean on a spec sheet:
- Torque is the twist the engine makes — what you feel pulling away and overtaking in a high gear.
- Power is torque multiplied by how fast it is being delivered. Peak power is almost always at higher rpm than peak torque, because the torque curve falls off more slowly than the rpm rises.
- Neither is a ranking on its own. A diesel with 400 Nm at 2,000 rpm makes 84 kW there; a petrol engine with 200 Nm at 7,000 rpm makes 147 kW.
Frequently Asked Questions
How do I convert torque to horsepower?
Horsepower = torque in lb·ft × rpm ÷ 5,252. In metric, kW = Nm × rpm ÷ 9,549. 400 Nm at 4,500 rpm is 188 kW, about 253 hp.
Why do horsepower and torque cross at 5,252 rpm?
Because hp = lb·ft × rpm ÷ 5,252. At 5,252 rpm the division cancels, so the two figures are equal. It is a property of the units, not of any engine — in metric units the curves do not cross there.
Is torque or horsepower more important?
They are the same thing viewed differently; power is torque times rpm. For acceleration what matters is power at the wheels across the rev range you use, which is why gearing lets a high-revving, low-torque engine out-accelerate a torquey one.