Top Speed Estimate Calculator

Work out top speed estimate instantly with clear inputs, formula shown and shareable results.

About Top Speed Estimate Calculator

Top speed is where available power equals the power absorbed by drag and rolling resistance. Because drag power rises with the cube of speed, doubling power raises top speed by only about 26% — which is why very high top speeds need enormous power.

Formula

Top speed

power = (0.5 rho Cd A v^2 + Crr m g) x v; solve for v

Worked example

With the default values below, Top Speed Estimate Calculator returns Estimated top speed of 144.00. Change any input above and every figure here is recalculated in your browser.

Inputs used

Power at the wheels: 150 kW
Drag coefficient: 0.31 Cd
Frontal area: 2.2 m²
Rolling resistance coefficient: 0.012

Results

Estimated top speed: 144.00 km/h
Power absorbed by drag at that speed: 26.73 kW
Drag area (Cd x A): 0.68 m²
Top speed: 89.48 mph

Step by step

1Values used
2Top speed
3Estimated top speed= 144.00 km/h
4Power absorbed by drag at that speed= 26.73 kW
5Drag area (Cd x A)= 0.68 m²
6Top speed= 89.48 mph

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why does top speed rise so slowly with power?

Drag power scales with v cubed, so speed scales with the cube root of power. Eight times the power gives twice the speed.

What is drag area?

Cd times frontal area. It is the honest comparison figure, since a low Cd on a large vehicle can still mean high drag.