Compare 2โ4 vehicles side by side in every common unit, reverse-solve for power or weight, and get estimated 0-60 and quarter-mile times.
Your Vehicles
Add 2โ4 vehicles. Each slot can solve for ratio, power, or weight โ pick the unknown from the dropdown and enter the other two.
Comparison & Ranking
Ranked best โ worst by power-to-weight (highest W/kg first). Bars are scaled to the best vehicle.
Benchmarks (illustrative)
Typical real-world ballparks for context โ not exact specs.
| Vehicle type | lb/hp | W/kg | Est. 0-60 (s) |
|---|---|---|---|
| Formula 1 car | ~1.7 | ~970 | ~2.5 |
| Superbike (1000cc) | ~2.5 | ~670 | ~3.0 |
| Sports sedan | ~9 | ~185 | ~4.5 |
| Family SUV | ~17 | ~100 | ~7.5 |
| Full-size pickup | ~20 | ~85 | ~8.5 |
Share & Saved Setups
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Worked Examples
Frequently Asked Questions
Why does power-to-weight matter more than raw horsepower?
Acceleration is force divided by mass. A 200 hp car weighing 2,000 lb will out-accelerate a 300 hp car weighing 4,000 lb, because each horsepower has less mass to move. Power-to-weight is the single best one-number predictor of straight-line pace.
Which unit should I use โ W/kg, hp/ton, or lb/hp?
They all express the same thing. W/kg (identical to kW/tonne) is the SI standard and what engineers publish. hp per US ton is common in American marketing; lb/hp is popular with drag racers because Hale’s ET formula uses it directly, and smaller numbers are better. This calculator shows all five at once.
How accurate are the 0-60 and quarter-mile estimates?
They use Hale’s empirical formulas, fitted to real drag-strip data: ET = 6.269 ร (lb/hp)โ , trap = 230 ร (hp/lb)โ , 0-60 โ 0.63 ร ET. They assume a proper launch, good traction, and a competent driver โ typically within ~5โ10% for conventional cars. Treat them as estimates, not guarantees.
Should weight include driver, fuel, and cargo?
For the most honest number, yes โ use curb weight plus ~180 lb driver plus fuel. A full 20-gallon tank adds ~120 lb. Comparisons are only fair if every vehicle uses the same convention.
Does power-to-weight predict handling or top speed?
No. It predicts acceleration only. Top speed is set by power vs aerodynamic drag; cornering by tires, suspension, and weight distribution. A light car with modest power can still be slow in a straight line but brilliant in corners.
Does a higher power-to-weight ratio always mean faster?
For straight-line acceleration, mostly yes โ but only “all else being equal”. Traction, gearing, aerodynamics, and power delivery matter. A high-ratio car with poor traction control or a peaky power band can lose to a lower-ratio car that puts power down cleanly. The ratio ranks potential, not guaranteed outcomes.
Is it fair to compare an EV against a gas car this way?
Roughly, yes โ but know the caveat. EVs deliver peak torque instantly and often sustain it, while gas engines quote peak horsepower at high RPM. Two vehicles with identical ratios will often see the EV launch harder. Battery weight also inflates EV curb weight, so the ratio understates the EV’s advantage off the line and overstates the gas car’s.
How does power-to-weight relate to 0-60 mph times?
It is the strongest single predictor: double the ratio and 0-60 typically drops substantially, though not by half, because traction and shifting eat some of the gain. As a rule of thumb, cars near 150 hp/ton run low-6-second 0-60 times; near 300 hp/ton, low-4s; near 500 hp/ton, under 3 seconds. Use it to estimate, then check instrumented tests for the real number.
Why do motorcycles have such extreme ratios?
Simple physics: a 450 lb sport bike with 150 hp works out to about 667 hp/ton โ supercar territory at a fraction of the price. Weight is the denominator, and motorcycles have almost none of it. That is also why rider weight matters so much on a bike: a 180 lb rider is a far larger percentage of total weight than in a car.
Why do trucks have such low power-to-weight ratios?
They are built to move weight, not to be light. A full-size truck might show 90โ120 hp/ton โ sluggish on paper โ but its tall gearing multiplies torque at the wheels, which is what actually moves a trailer. Power-to-weight predicts unloaded acceleration; towing ability depends on torque, gearing, cooling, and chassis ratings too.
Limitations
Power to Weight Ratio Calculator
A power to weight ratio calculator tells you how much power is available to move each unit of a vehicle’s weight โ the single number that best predicts how a vehicle accelerates. Enter the horsepower and the weight, and it returns horsepower per ton (and the metric equivalent, watts per kilogram).
It is the fair way to compare acceleration potential across cars, trucks, motorcycles, and EVs that look nothing alike on paper.
How to use this power to weight ratio calculator
- Enter the power in horsepower (or kilowatts โ the calculator converts automatically). Use the manufacturer’s rated output, ideally crank horsepower measured on the same standard for every vehicle you compare.
- Enter the weight in pounds (or kilograms). Use curb weight โ the vehicle with all fluids and a full tank, no driver.
- Read the result in hp per ton and W/kg. Use the Solve for dropdown in each vehicle card to pick the unknown: Ratio finds W/kg from your power and weight, Power finds the horsepower needed to match the best vehicle’s ratio at your weight, and Weight finds the weight needed to match the best vehicle’s ratio at your power.
- Compare vehicles side by side. Run the numbers for each candidate with the same weight and power standards, and the ranking tells you which one should accelerate hardest, all else being equal.
Formulas with worked examples
Horsepower per ton
hp/ton = horsepower รท weight in tons
Worked example: 300 hp, 3,500 lb curb weight.
3,500 รท 2,000 = 1.75 tons
300 รท 1.75 = 171.4 hp/ton
The US ton (2,000 lb) is used here. If you see a figure in “hp per metric tonne”, it will differ slightly โ always check which ton the source used.
Metric: watts per kilogram
W/kg = power in watts รท weight in kilograms
Worked example: the same 300 hp, 3,500 lb vehicle.
300 hp ร 745.7 = 223,710 W = 223.7 kW
3,500 lb ร 0.453592 = 1,587.6 kg
223,710 รท 1,587.6 = 140.9 W/kg
W/kg is the SI unit and the fairest cross-border comparison โ it removes the US-ton/metric-tonne ambiguity entirely.
Common mistakes
- Using gross vehicle weight instead of curb weight. Curb weight (empty, fueled) is the standard. Gross vehicle weight rating includes maximum payload and makes the ratio look far worse than it drives.
- Mixing crank horsepower with wheel horsepower. Manufacturer figures are crank (engine) horsepower; dyno results are wheel horsepower, typically 10โ15% lower. Comparing one car’s crank figure against another’s wheel figure invalidates the comparison.
- Mixing hp(I) and hp(M). Imperial horsepower is 745.7 W; metric (PS/CV) horsepower is 735.5 W. European brochures often quote PS โ a “300 PS” car is about 296 hp(I). Convert before comparing.
- Ignoring driver and fuel weight. A 180 lb driver plus a full tank can add 250+ lb. For track-day or drag comparisons, add driver weight to curb weight for a realistic figure.
- Forgetting cargo and passengers. A truck’s ratio with a loaded bed or four passengers is far lower than its brochure number. Recalculate for the actual load if you care about real-world performance.