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Horsepower Calculator

Calculate an engine's horsepower output from its torque and RPM using the standard automotive formula.

About the Horsepower Calculator

Calculate an engine's horsepower output from its torque and RPM (engine speed) using the standard automotive formula.

How the Horsepower Calculator works

Torque and horsepower are related but different things: torque is the twisting force an engine produces, while horsepower is the rate at which that work is done — so horsepower depends on both torque and how fast the engine is spinning. This is why a high-revving small engine can produce similar horsepower to a low-revving large engine with much higher torque.

How to use the Horsepower Calculator

  1. Enter the torque value and choose its unit (lb-ft or Nm).
  2. Enter the engine RPM at which that torque was measured.
  3. Press Calculate to see the horsepower output.

Tips for the Horsepower Calculator

  • Torque and horsepower curves always cross at exactly 5,252 RPM when torque is measured in lb-ft — this is a mathematical property of the formula, not a coincidence.

Formula used by the Horsepower Calculator

HP = (Torque(lb-ft) × RPM) ÷ 5252

Example: Horsepower Calculator

300 lb-ft of torque at 4,000 RPM

  • Torque: 300 lb-ft
  • RPM: 4,000

Result: ≈ 228.5 HP

HP = (300 × 4,000) ÷ 5,252 ≈ 228.5 horsepower.

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