Horsepower Calculator
Turn torque and engine speed into horsepower — the classic dyno formula — and see the result in kW, metric horsepower (PS) and watts at once. Includes worked steps and a reference table for common torque/RPM combinations.
TheCalculators — Horsepower Calculator
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Horsepower
285.6 hp
300 lb-ft × 5,000 RPM ÷ 5252 · 213 kW (289.6 PS)
Same power in every unit
- Mechanical Horsepower
- 285.61 hp
- Kilowatts
- 212.98 kW
- Metric Horsepower (PS/cv)
- 289.57 PS
- Watts
- 212,976
- BTU per Hour
- 726,704
- Torque Used
- 300 lb-ft (406.7 N·m)
Solution steps
- 1FormulaHP = Torque (lb-ft) × RPM ÷ 5252
- 2Convert torque if neededAlready in lb-ft: 300
- 3Multiply by RPM300 × 5,000 = 1,500,000
- 4Divide by 52521,500,000 ÷ 5252 = 285.61 hp
- 5Convert to kW285.61 hp × 0.7457 = 212.98 kW
Horsepower at common torque/RPM points
5252 is the RPM where torque (lb-ft) and horsepower are numerically equal — below it torque exceeds hp, above it hp exceeds torque.
This is the definition-based relation for rotating shaft power. Real drivetrain output at the wheels is 10–20% lower due to friction losses.
Most useful next
Formula
HP = Torque(lb-ft) × RPM ÷ 5252 · kW = HP × 0.7457 · PS = HP × 1.0139
- • Horsepower by definition is 550 ft·lb/s; rotating power = torque × angular speed.
- • Combining them gives HP = T × RPM ÷ 5252 (5252 hides the 33,000 ft·lb/min and 2π factors).
- • Multiply by 0.7457 for kilowatts, or 1.0139 for metric horsepower (PS).
Pro tips
- • Torque wins the launch, horsepower wins the top end — hp rises with RPM at constant torque.
- • Electric motors make peak torque at 0 RPM, so their kW rating matters more than "hp".
- • The 5252 crossover is why engines feel "torquey" low and "powerful" high in the rev range.
FAQ
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