Braking distance is how far a vehicle travels while decelerating to a stop, set by speed and tire grip.
Where
| v | Speed at the start of braking |
| μ (mu) | Tire-to-road friction coefficient (about 0.7 dry, 0.4 wet) |
| g | Gravity, 9.81 m/s² (32.2 ft/s²) |
Worked example
At 27 m/s (about 60 mph) on dry asphalt: 27² ÷ (2 × 0.7 × 9.81) = 729 ÷ 13.7, about 53 m of braking.
FAQ
Why does braking distance increase so much at higher speeds? Braking distance scales with the square of speed, not speed itself, so doubling speed roughly quadruples stopping distance, which is why highway speeds require dramatically more following distance than city speeds.
Does this formula account for road conditions like rain or ice? No, the basic formula assumes a standard dry-pavement friction value. Wet, icy, or gravel surfaces reduce available friction significantly, increasing actual stopping distance well beyond the dry-condition prediction.
Use the Brake Distance calculator to include reaction distance.