Guide
Car hp calculator: torque, trap speed and ET to horsepower
Three quick converters for horsepower. Everything runs in your browser. When you have a power figure, take it to the 0-60 calculator.
Torque and rpm to hp
Estimated power: –
Trap speed and weight to hp
Estimated power: –
Elapsed time and weight to hp
Estimated power: –
The formulas
- Torque to hp: hp = torque (lb-ft) × rpm ÷ 5252. At 5,252 rpm, hp and lb-ft are numerically equal. 400 lb-ft at 4,500 rpm is about 343 hp.
- Trap speed to hp: hp ≈ weight × (trap speed ÷ 234)³.
- ET to hp: hp ≈ weight × (6.269 ÷ ET)³.
These are rules of thumb. Results depend on whether the source used flywheel or wheel horsepower and whether the weight included the driver; drivetrain loss is commonly quoted at 10 to 20 percent. To find the power needed for a target time instead, use the Power needed for a target time panel in the 0-60 calculator. For the math behind it, see the 0-60 formula guide and quarter mile to 0-60.
Worked examples
- Torque: 400 lb-ft at 4,500 rpm is 400 × 4,500 ÷ 5,252, about 343 hp.
- Trap speed: a 3,500 lb car trapping at 100 mph is 3,500 × (100 ÷ 234)³, about 273 hp.
- Elapsed time: a 3,500 lb car running a 13.5 second quarter mile is 3,500 × (6.269 ÷ 13.5)³, about 350 hp.
Which estimate should you trust?
Trap speed is usually the better guide to power, because it is measured at the end of the run and depends less on how well the car launched. Elapsed time is easier to measure but also reflects tires, traction and driver skill, so it can read low or high for the same engine. When you have both, compare them: a big gap points to a launch problem, not a power problem.
Power unit conversions
1 hp is 0.7457 kW and about 1.0139 PS (metric horsepower). To go from kW to hp, multiply by 1.341. The 0-60 calculator accepts hp, kW or PS, so you can enter a figure in whichever unit you have.
Related guides and tools
Last updated: October 24, 2026. Estimates only; see the Terms.