Work out top speed estimate instantly with clear inputs, formula shown and shareable results.
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.
Top speed
power = (0.5 rho Cd A v^2 + Crr m g) x v; solve for v
Drag power scales with v cubed, so speed scales with the cube root of power. Eight times the power gives twice the speed.
Cd times frontal area. It is the honest comparison figure, since a low Cd on a large vehicle can still mean high drag.