Horsepower and torque are linked by engine speed: power is torque times rotational speed. That is why horsepower and torque curves (in lb·ft) always cross at 5,252 rpm.
How to use the Torque to Horsepower Calculator
- Torque
- Engine speed
- Every result field is editable: type into Power or any other result and Engine speed plus every other field update to match.
Results update as you type, and every field accepts the units shown in its menu.
How it works
Torque is converted to newton-metres, rpm to radians per second, and the two are multiplied to give watts.
Inputs explained
| Field | What to enter |
|---|---|
| Torque | Units: lbf·ft, N·m, kgf·m |
| Engine speed | In rpm |
What each result means
- Power = [Torque] × 2 × pi × [Engine speed] ÷ 60
- In kilowatts = [Torque] × 2 × pi × [Engine speed] ÷ 60
Example values
How the main result changes when Engine speed changes and everything else stays at the example values above:
| Engine speed (rpm) | Power (hp) |
|---|---|
| 2,626 | 150 |
| 3,939 | 225 |
| 5,252 | 299.99 |
| 6,565 | 374.99 |
| 7,878 | 449.99 |
| 10,504 | 599.99 |
Formula
hp = torque (lb·ft) × rpm ÷ 5,252P (W) = T (N·m) × 2π × rpm ÷ 60Worked example
Inputs — Torque: 300 lbf·ft; Engine speed: 5,252 rpm.
Results — Power = 299.99 hp; In kilowatts = 223.71 kW.
Frequently asked questions
Why do torque and hp curves cross at 5,252 rpm?
Because hp = lb·ft × rpm ÷ 5,252, they are equal at that speed.
How much hp is 400 N·m at 6,000 rpm?
About 337 hp (251 kW).
What formula does the Torque to Horsepower Calculator use?
hp = torque (lb·ft) × rpm ÷ 5,252.