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The standard formula converts foot-pounds of torque and RPM to horsepower. This gives brake horsepower (BHP) at the crankshaft.
HP = (Torque × RPM) / 5252Empirical formulas estimate flywheel HP from vehicle weight and quarter-mile elapsed time (ET). Assumes average traction and driver skill.
HP ≈ Weight / (ET / 5.825)³1 HP = 0.7457 kW = 1.014 PS (metric horsepower). Wheel horsepower (WHP) is typically 10–20% less than crank HP due to drivetrain losses.
kW = HP × 0.7457Updated: July 2026
HP = (350 × 5500) / 5252 = 366 BHP. Note HP and torque curves cross at 5252 RPM by definition of the formula.
Estimated flywheel HP ≈ 3200 / (13.2/5.825)³ ≈ 320 HP. Actual may vary ±10% based on traction, gearing, and altitude.
300 HP × 0.7457 = 223.7 kW. Useful for comparing US-spec engines to European kW power ratings.
Dyno charts should specify WHP or BHP. Comparing a 350 WHP dyno result to a manufacturer's 400 HP crank rating is misleading — add 15% to WHP to approximate crank HP.
HP varies across the RPM range. Calculate HP at multiple RPM points to map the full power curve. Peak HP and peak torque occur at different RPM on most engines.
Horsepower connects engine torque, RPM, and vehicle performance. Calculate brake horsepower from dyno torque readings, estimate from quarter-mile elapsed time and weight, or convert between HP, kW, and PS metric units.