Why is this only theoretical?

Real top speed is limited by gearing (the engine may hit the rev limiter before aerodynamic limit), electronic speed limiters (many cars limited to 155mph), tyre speed ratings, and available road length. This calculator shows the aerodynamic limit only.

What is a typical Cd value?

Modern cars range from 0.22 (very aerodynamic like Tesla Model 3) to 0.40+ (boxy SUVs). Average is about 0.30-0.33. Sports cars are typically 0.28-0.35.

What is frontal area?

Frontal area is the cross-section of the car facing the wind, typically 1.8-2.2 m² for cars and 2.5-3.0 m² for SUVs. It can be estimated as roughly 80% of width x height.

What limits a car top speed?

Three main factors: aerodynamic drag (increases with the cube of speed), engine power, and electronic limiters. Most German cars are limited to 155 mph (250 km/h) by agreement. Without a limiter, top speed depends on having enough power to overcome drag at that speed.

Is the drag coefficient or frontal area more important?

Both matter equally since drag force = 0.5 x air density x Cd x frontal area x speed squared. A sleek sports car may have a low Cd (0.28) but small area, while an SUV has higher Cd (0.35) and much larger area. For top speed, reducing either has the same proportional effect.

CarCalcs

Top Speed Calculator

Estimate theoretical top speed from power, drag, and frontal area.

Engine Power

Drag Coefficient (Cd)

Typical: 0.25-0.40

Frontal Area

~80% of width x height

How We Calculate This

At top speed, all engine power overcomes aerodynamic drag: P = 0.5 x air density x Cd x A x v³. Solving for v gives theoretical top speed.

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Actual figures may vary based on driving conditions, vehicle specifications, and other factors.