Engine Horsepower Calculator
Calculate shaft power from torque and RPM, or estimate power with Hale quarter-mile models.
Formula
Torque: P = τ × 2πRPM/60 W. Hale: hp = lb/(s/5.825)³ or lb × (mph/234)³.
Race mass including driver: 3,300 lb · Quarter-mile elapsed time: 14 s · Quarter-mile trap speed: 100 mph · Shaft torque: 250 lbf·ft · Mechanical horsepower ≈ (250 lbf·ft × 1.355817948 N·m/lbf·ft)×(5,000)×2×pi÷60÷745.6998715822702 · Power ≈ (237.9994435)×0.7456998715822702
How to use
- Choose a method.
- Fill torque and RPM, or race mass plus quarter-mile time or trap speed.
- Read mechanical hp and kW; other inputs are unused.
Examples
- 3200 lb with 11.65 s or 117 mph gives a Hale estimate of 400 hp.
Frequently asked questions
Must torque and RPM match?
Yes. Use torque measured at the entered RPM, not peak torque at a different RPM.
What race distance is assumed?
Exactly one quarter mile (402.336 m), not a 400 m run. Mass includes driver and load.
Are track estimates dyno measurements?
No. Hale estimates depend on traction, gearing and conditions; they do not establish wheel or crank power precisely.
Sources
Updated: