Horsepower from 400 lb·ft at 4000 RPM
400 lb·ft of torque at 4,000 RPM equals approximately 305 horsepower.
How to use this tool
- Enter the engine torque in pound-feet (from a dyno or spec sheet).
- Enter the RPM at which that torque figure is measured.
- The calculator applies HP = Torque × RPM ÷ 5,252 and returns horsepower.
A diesel or truck engine making 400 lb·ft of torque at 4,000 RPM produces about 305 horsepower.
Frequently asked questions
- What is the formula for horsepower from torque?
- HP = Torque (lb·ft) × RPM ÷ 5,252. The constant 5,252 comes from unit conversion: one horsepower equals 33,000 ft·lb/min, and 33,000 ÷ (2π) ≈ 5,252.
- Why do HP and torque curves cross at 5,252 RPM?
- Because at exactly 5,252 RPM the divisor equals the multiplier, so HP = Torque numerically. On a dyno chart the two curves always intersect at that engine speed.