Power-to-Weight Ratio Calculator
Enter your car's horsepower and weight to get its power-to-weight ratio in every common unit — hp per ton, hp per lb, lb per hp, hp per kg, and kW per tonne. Then verify how it actually accelerates with real GPS timing.
Bottom line: power-to-weight ratio is the strongest single predictor of how quickly a car accelerates. Divide horsepower by weight to compare any two cars fairly — this calculator returns hp/ton, hp/lb, lb/hp, hp/kg, and kW/tonne at once so the number matches whatever spec sheet you are reading.
How to Use the Calculator
- Enter your vehicle weight in pounds — curb weight, or add fuel and driver for race weight
- Enter your horsepower — flywheel (crank) or wheel HP
- The calculator returns hp/ton, hp/lb, lb/hp, hp/kg, and kW/tonne, plus an approximate performance segment
The Formulas
- hp/ton = HP ÷ (Weight ÷ 2000) — horsepower per US short ton (2,000 lb)
- kW/tonne = (HP × 0.7457) ÷ (Weight × 0.4536 ÷ 1000) — kilowatts per metric tonne
Conversions used: 1 lb = 0.4536 kg, and 1 hp = 0.7457 kW. The raw hp/lb, lb/hp, and hp/kg ratios are simply horsepower divided by the weight expressed in each unit.
Which "Ton" Do We Mean?
The hp/ton figure here uses the US short ton (2,000 lb), the convention most US and UK enthusiasts quote. Europe and manufacturers often use the metric tonne (1,000 kg) as bhp/tonne or kW/tonne — so this calculator gives you both, plus the raw hp/lb and hp/kg ratios, to avoid apples-to-oranges comparisons.
Flywheel vs Wheel Horsepower
The ratio is only as honest as the horsepower you feed it. Flywheel (crank) HP is what manufacturers advertise; wheel HP is what a dyno measures at the tires, after drivetrain losses (typically 10–15% for a manual, more for an automatic or AWD). Using wheel HP gives a more realistic ratio for predicting acceleration — just make sure you compare like with like.
Typical Power-to-Weight by Segment
Approximate hp per US short ton (2,000 lb). Real numbers vary by trim, weight, and how power is quoted.
| Segment | Approx. hp/ton | Typical Examples |
|---|---|---|
| Economy | ~80–120 | Compact commuters, base sedans, small crossovers |
| Warm / Sporty | ~120–150 | Sport trims, warm hatches, entry sport sedans |
| Hot Hatch | ~150–200 | Golf R, Civic Type R, GR Corolla |
| Sports Car | ~200–280 | Cayman, Supra, Mustang GT, M2 |
| Supercar | ~300–450 | 911 Turbo, R8, McLaren GT |
| Hypercar | 500+ | Chiron, SF90, hyper-EVs |
Ratio Isn't the Whole Story — Verify with GPS
Power-to-weight sets your ceiling, but traction, gearing, drivetrain losses, and launch technique decide the real 0-60. FastTrack measures your real 0-60 within ±0.02 seconds using GPS Doppler velocity fused with a 100Hz accelerometer — Dragy-class accuracy, free. Run a few passes and compare your actual acceleration against what your ratio predicts.
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Frequently Asked Questions
What is a good power-to-weight ratio?
For a US short ton (2,000 lb), roughly 80–120 hp/ton is economy, 150–200 hp/ton is hot-hatch quick, 200–280 hp/ton is genuine sports-car territory, 300–450 hp/ton is supercar, and 500+ hp/ton is hypercar. Higher is better — more power moving less mass means faster acceleration. Anything above about 200 hp/ton feels seriously fast on the street.
Should I use curb weight or race weight?
Use whichever matches the number you are comparing against. Manufacturers usually quote power-to-weight against dry or curb weight, but the weight that actually accelerates includes fuel, fluids, and driver. For a real-world figure, add roughly 150–200 lb for the driver plus a full tank to curb weight — that race weight is what your GPS 0-60 will actually reflect.
hp per ton vs hp per kg — which do people use?
It depends on the market. US and UK enthusiasts usually quote hp per ton (here, the US short ton of 2,000 lb) because it lands on intuitive whole numbers. Europe and manufacturers often use kW per tonne or bhp per tonne (metric tonne = 1,000 kg). hp per kg and hp per lb are the raw ratios engineers use. This calculator gives you all five so you can compare against any spec sheet.
Does power-to-weight predict 0-60 time?
Power-to-weight is the single strongest predictor of straight-line acceleration, but it is not the whole story. Traction, gearing, drivetrain losses, tire grip, and launch technique all move the real number. Two cars with identical hp/ton can post very different 0-60 times if one puts its power down cleanly and the other spins. Use the ratio to set expectations, then measure the real result.
How do I measure my real 0-60?
FastTrack measures your real 0-60 for free using your phone. It fuses GPS Doppler velocity with a 100Hz accelerometer, producing 0-60 times within ±0.02 seconds — inside the range of a dedicated Dragy or RaceBox, at no cost. Run a few passes on a safe, empty stretch and compare your actual acceleration against what your power-to-weight ratio predicts.