Horsepower Calculator

Calculate horsepower from quarter mile times, trap speed, or torque. Estimate performance metrics and power-to-weight ratios.

Power Results

Horsepower

1879 HP

320 lb-ft torque

1/4 Mile Time13.50 sec
Trap Speed578 mph
HP/Ton1074

Calculation Method

Input Values

Performance Results

Horsepower

1879

HP

Torque

320

lb-ft

1/4 Mile

13.50

seconds

Trap Speed

578

mph

Power-to-Weight

1074 HP/ton

Est. 0-60 mph

3.4 sec

HP per lb

0.537

Formulas Used

From Quarter Mile Time

HP = (Weight / ET³) × 1320.61

Buschur formula

From Trap Speed

HP = Weight × (Speed / 234)³

From Torque

HP = (Torque × RPM) / 5252

HP and Torque cross at 5252 RPM

Power-to-Weight

HP/ton = (HP / Weight) × 2000

Performance Class Reference

ClassHP RangeHP/Ton1/4 Mile0-60 mph
Economy100-15050-8017-19s10-13s
Family Sedan150-25080-12015-17s7-10s
Sports Car250-400150-25013-15s5-7s
Muscle Car400-600200-30012-13s4-5s
Supercar600-800300-40010-12s3-4s
Hypercar800+400+<10s<3s

Power Unit Conversions

1 HP (mechanical)

= 745.7 Watts

1 HP (metric/PS)

= 735.5 Watts

1 kW

= 1.341 HP

1 lb-ft

= 1.356 Nm

Quick Answer

Horsepower = (Torque x RPM) / 5252. This formula uses torque in lb-ft. Example: 300 lb-ft at 4000 RPM = (300 x 4000) / 5252 = 228 HP. Conversions: 1 HP = 0.746 kW = 1.014 PS (metric HP). Peak HP and peak torque occur at different RPMs; they cross at 5252 RPM.

Key Facts

  • HP = (Torque in lb-ft x RPM) / 5252
  • Torque and HP curves cross at exactly 5252 RPM
  • 1 HP = 745.7 watts = 0.746 kW
  • 1 HP = 1.014 PS (metric horsepower)
  • Brake HP (BHP) = measured at engine
  • Wheel HP (WHP) = measured at wheels (10-15% drivetrain loss)
  • 1 HP = ability to lift 550 pounds 1 foot in 1 second
  • Torque accelerates; HP determines top speed

Frequently Asked Questions

Horsepower (HP) measures the rate at which work is done. One mechanical horsepower equals 550 foot-pounds per second or 745.7 watts. In cars, it determines how fast the engine can move the vehicle, affecting acceleration and top speed.
Torque is rotational force (measured in lb-ft or Nm), while HP is the rate of applying that force. HP = (Torque × RPM) / 5252. Torque provides initial acceleration; HP maintains speed. "Torque wins races, HP sells cars."
Crank HP (gross) is measured at the engine crankshaft. Wheel HP (WHP) is measured at the wheels after drivetrain losses. Typically WHP is 15-20% less due to transmission and differential friction. Dyno numbers are usually WHP.
Use the formula: ET = (Weight/HP)^(1/3) × constant. Weight should include driver. Actual times vary with traction, altitude, temperature, and driver skill. Professional times use weight with driver and half tank of fuel.
Economy cars: 50-80 HP/ton. Sports cars: 150-250 HP/ton. Performance cars: 250-400 HP/ton. Supercars: 400+ HP/ton. Formula 1: ~1000 HP/ton. Higher ratios mean faster acceleration.