Engine Horsepower Calculator
Estimate engine horsepower using different calculation methods based on torque, RPM, engine displacement, or dynamometer results.
Understanding Horsepower Calculations
Torque and RPM Method
This is the most accurate method when you know the engine's torque output and RPM. The formula used is: HP = Torque (lb-ft) × RPM ÷ 5252 The constant 5252 is derived from the relationship between torque, power, and rotational speed.
Engine Displacement Method
This method provides a rough estimate based on engine size and type. Different engine types typically produce different power outputs per liter of displacement:
- Standard engines: ~75 HP/L
- Performance engines: ~100 HP/L
- Turbocharged engines: ~150 HP/L
- Supercharged engines: ~130 HP/L
Quarter Mile Method
This method estimates horsepower based on a vehicle's quarter-mile elapsed time (ET) and weight: HP = (Weight × 0.00658) ÷ (ET)³ This formula accounts for the relationship between power, weight, and acceleration.
Trap Speed Method
This method uses the trap speed (the speed at the end of a quarter-mile run) and vehicle weight: HP = (Weight × Speed³) ÷ 1,320,000 Trap speed is often considered more reliable than elapsed time for estimating horsepower.