Horsepower Comparison Calculator
Compare two vehicles by horsepower, weight and power-to-weight ratio.
Raw horsepower alone doesn't decide which car is quicker — weight matters just as much. This tool compares two vehicles by power-to-weight ratio, the truest single measure of performance potential.
How the Comparison Works
A 300 HP car at 3,200 lb (0.094 hp/lb) actually out-accelerates a 400 HP car at 4,400 lb (0.091 hp/lb), despite having 100 fewer horsepower — because it carries less weight per horsepower.
How to Use This Calculator
- Enter Car 1's horsepower and weight.
- Enter Car 2's horsepower and weight.
- See which has the better power-to-weight ratio.
Worked Example
Why Power-to-Weight Decides Acceleration
Acceleration depends on how much power is available to move each pound of car, not on raw horsepower. A lighter car with less power can out-accelerate a heavier, more powerful one — which is the whole philosophy behind lightweight sports cars. Comparing two vehicles by hp/lb (or hp per ton) strips away the marketing headline numbers and reveals which actually performs better.
What Power-to-Weight Doesn't Capture
Power-to-weight is the best single number, but real-world results also depend on traction (AWD launches harder), aerodynamics at speed, gearing, torque delivery, and where in the rev range the power arrives. Two cars with identical hp/lb can still feel different if one makes its power low and broad and the other only at high RPM. Use this comparison as the primary filter, then weigh those secondary factors.
Making the Comparison Fair
Most spec-sheet comparisons are wrong before the arithmetic starts, because the two figures were not measured the same way. Check these four before you compare anything.
| Check | The trap | Size of the error |
|---|---|---|
| Same power unit | One car quoted in PS, the other in bhp | 1.4% |
| Same measurement point | One figure from a rolling road, the other from the brochure | 11–23% |
| Same rating standard | Pre-1972 SAE gross against modern SAE net | 15–25% |
| Same weight basis | Dry weight against curb weight, or curb against curb-plus-driver | 3–8% |
Quick fixes: convert PS to bhp with bhp to PS, bring a dyno figure back to the crank with whp to hp, and use curb weight for both cars unless you are adding a driver to both.
Benchmark Bands
Where a given ratio places a car, in all three units you are likely to meet.
| hp/lb | hp per US ton | kW/tonne | Category |
|---|---|---|---|
| 0.030–0.045 | 60–90 | 49–74 | Economy car |
| 0.045–0.060 | 90–120 | 74–99 | Mainstream sedan / SUV |
| 0.060–0.085 | 120–170 | 99–140 | Warm hatch, quick daily |
| 0.085–0.110 | 170–220 | 140–181 | Hot hatch, sports car |
| 0.110–0.150 | 220–300 | 181–247 | Performance car |
| 0.150–0.250 | 300–500 | 247–411 | Supercar |
| > 0.250 | > 500 | > 411 | Hypercar, track special |
Working in metric instead? The kW per tonne calculator uses the same bands in kilowatts, and horsepower per ton covers the imperial ton conversions.
When the Lower-Powered Car Wins Anyway
Power-to-weight is the best single predictor, but it is not the whole picture. Four things regularly overturn it:
- Traction. Above roughly 220 hp per ton on a rear-drive car, launch grip decides the result rather than power. An all-wheel-drive car with a worse ratio can still leave first.
- Where the power lives. A broad, flat torque curve beats a peaky one in real driving, because you spend most of your time between gears rather than at the power peak.
- Gearing. Short gearing multiplies wheel torque and can beat a numerically better ratio over a short distance — while costing top speed.
- Aerodynamics. Irrelevant below about 60 km/h, dominant above 150. Two cars with identical ratios can have very different top speeds because drag scales with the cube of velocity.
A useful sanity check: convert the ratio into an expected time with the 0–60 mph calculator or quarter mile calculator. If a car's real-world times sit far off what its ratio implies, one of the four factors above is doing the work.
Power-to-Weight Comparison Examples
| Car | HP | Weight | hp/lb |
|---|---|---|---|
| Lightweight sports | 300 | 2,800 | 0.107 |
| Muscle car | 450 | 4,000 | 0.113 |
| Heavy GT | 400 | 4,400 | 0.091 |
For context on where any of these figures sit against the wider market, average car horsepower covers fifty years of EPA data on how much power a typical new car actually has.
Frequently Asked Questions
Compare their power-to-weight ratios (horsepower ÷ weight), not just raw horsepower. The higher ratio indicates better acceleration potential.
Yes. If it's light enough, a lower-horsepower car can have a better power-to-weight ratio and out-accelerate a more powerful but heavier car.
Use the same basis for both cars. Wheel horsepower is most realistic, but as long as both figures are measured the same way, the comparison is fair.
No. It predicts potential, but real-world results also depend on traction, gearing, aerodynamics, and transmission type.
Around 0.05 hp/lb is an economy car, 0.1 hp/lb is a quick sports car, and supercars exceed 0.2 hp/lb.