Air Resistance At Speed Calculator

Work out air resistance at speed instantly with clear inputs, formula shown and shareable results.

About Air Resistance At Speed Calculator

Drag force is dynamic pressure times drag area: half rho v squared times Cd times A. Force rises with the square of speed and power with the cube, which is the fundamental reason motorway fuel consumption climbs so steeply above 100 km/h.

Formula

Aerodynamic drag

F = 0.5 x rho x v^2 x Cd x A; P = F x v

Worked example

With the default values below, Air Resistance At Speed Calculator returns Aerodynamic drag force of 505.31. Change any input above and every figure here is recalculated in your browser.

Inputs used

Speed: 120 km/h
Drag coefficient: 0.33 Cd
Frontal area: 2.25 m²
Air density: 1.225 kg/m³

Results

Aerodynamic drag force: 505.31 N
Power to overcome drag: 16.84 kW
Dynamic pressure: 680.56 Pa
Drag force at 100 km/h: 350.91 N

Step by step

1Values used
2Aerodynamic drag
3Aerodynamic drag force= 505.31 N
4Power to overcome drag= 16.84 kW
5Dynamic pressure= 680.56 Pa
6Drag force at 100 km/h= 350.91 N

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 10% more speed cost 33% more power?

Force scales with v squared and power with v cubed. 1.1 cubed is 1.33, so a tenth more speed needs a third more power.

Does air density matter much?

Yes. At altitude or on a hot day density falls, reducing drag by a few percent — one reason speed records are set at high altitude.