Model vehicle speed using power, aero drag, gearing, slope, and resistance. See realistic limits instantly. Export results, review charts, and test engineering scenarios confidently.
Use this sample set to test the calculator quickly.
| Parameter | Example Value | Unit |
|---|---|---|
| Engine Power | 320 | hp |
| Drivetrain Loss | 15 | % |
| Drag Coefficient | 0.31 | Cd |
| Frontal Area | 2.05 | m² |
| Vehicle Mass | 1500 | kg |
| Rolling Resistance | 0.013 | Crr |
| Air Density | 1.225 | kg/m³ |
| Road Grade | 0 | % |
| Headwind | 0 | km/h |
| Redline | 6800 | rpm |
| Top Gear Ratio | 0.82 | - |
| Final Drive Ratio | 3.55 | - |
| Tire Diameter | 0.67 | m |
Available wheel power
Pwheel = Pengine × (1 − drivetrain loss)
Aerodynamic drag force
Fd = 0.5 × ρ × Cd × A × Vair2
Vair = Vvehicle + headwind
Rolling resistance force
Fr = m × g × Crr × cos(θ)
Grade force
Fg = m × g × sin(θ)
Total power required
Prequired = (Fd + Fr + Fg) × Vvehicle
Gear-limited speed
Vgear = [RPMredline ÷ (top gear × final drive)] × π × tire diameter ÷ 60
Final estimated top speed
Top Speed = min(Power-Limited Speed, Gear-Limited Speed)
This model estimates steady-state top speed. It does not model lift, rev limit strategy, tire growth, wheel slip, crosswind, or transient acceleration.
It estimates steady-state vehicle top speed by comparing available wheel power against aerodynamic drag, rolling resistance, road grade, and gearing limits in top gear.
A vehicle can hit a speed ceiling because power is insufficient, or because gearing reaches redline first. The real top speed is whichever limit happens earlier.
Yes. Aerodynamic drag rises strongly with airspeed. Even a moderate headwind increases effective air velocity and can reduce top speed noticeably.
An uphill grade adds a continuous force the engine must overcome. A downhill grade does the opposite and can raise the estimated speed.
Enter crank power if you know engine output. Then use drivetrain loss to estimate wheel power. If you already know wheel power, set drivetrain loss to zero.
Yes. Tire diameter changes wheel circumference, which changes road speed for a given engine rpm. Larger tires usually raise gear-limited top speed.
No. Real outcomes depend on rev limit strategy, tire deformation, drivetrain heat, road surface, aero lift, wind angle, and manufacturer calibration. Use the result as a strong estimate.
Yes. Change power, drag coefficient, gearing, tire diameter, or weight-related inputs to compare setups and see which change matters most.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.