Horsepower Calculator
This is a track-data-derived approximation (the Hale/Bretterton-Ward formulas), not a dyno measurement — it assumes ideal traction and gearing, and doesn't account for aerodynamic drag, driveline loss, or launch technique. Use your official timing-slip trap speed, not a speedometer reading, for the most accurate estimate.
Free horsepower calculator estimating rear-wheel horsepower from a quarter-mile trap speed or elapsed time (ET) and vehicle weight, using the standard drag-racing formulas.
How it works
- Choose whether you're calculating from trap speed or elapsed time (ET)
- Enter your vehicle's weight (with driver) and the trap speed or ET
- See the estimated horsepower instantly
Frequently asked questions
How accurate is this?
For a well-hooked street car with a decent launch on a prepped surface, these formulas are typically within a few percent — but they assume ideal traction and gearing, and don't account for aerodynamic drag, driveline loss, or launch technique. Track conditions and driving skill are the biggest sources of real-world variance.
Should I use my speedometer reading for trap speed?
No — use the trap speed from an official timing slip if you have one. Speedometers are known to be inaccurate at high speeds, which throws off the calculation.
From the blog
Update history
- 2026-09-02 Launched: horsepower calculator with trap-speed and ET modes, folding in Engine Horsepower Calculator as the same underlying tool. Entirely client-side.