Calculator
Top Speed Calculator
Estimate a car's drag-limited top speed from its power, weight, drag coefficient and frontal area, and see the power needed for 200, 250 or 300 km/h.
Air drag stops this car at about 273 km/h (170 mph), with 190 kW reaching the wheels.
Power needed to hold a speed
| km/h | mph | hp |
|---|---|---|
| 100 | 62 | 21 hp |
| 150 | 93 | 58 hp |
| 200 | 124 | 125 hp |
| 250 | 155 | 233 hp |
| 300 | 186 | 392 hp |
| 350 | 217 | 613 hp |
How the estimate works
At top speed all the power that reaches the wheels goes into pushing air and rolling the tyres: P = ½ ρ Cd A v³ + Crr m g v. Air drag grows with the cube of speed, so doubling power only raises top speed by about 26%. Weight matters much less here than for acceleration.
The calculator assumes sea-level air (1.225 kg/m³), road tyres (Crr 0.012) and the drivetrain loss you set, and solves for the speed where the two sides are equal. It ignores gearing: a car that hits its rev limiter in top gear, or an electronic 250 km/h limiter, stops earlier.
Typical Cd and frontal area
- Modern saloon or hatchback — Cd 0.26-0.32, 2.1-2.3 m²
- Sports car — Cd 0.30-0.36, 1.9-2.1 m²
- SUV — Cd 0.33-0.40, 2.6-3.0 m²
- Car with a big wing or open wheels — Cd 0.40 or more
Drivetrain loss: about 10-12% for front- or rear-wheel drive with a manual, 15-20% for all-wheel drive or an automatic.
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