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Stopping Distance Calculator

Stopping distance calculator finds the distance your car travels before it comes to a stop.

Clear
Total stopping distance110.553 m362.7 ft
Thinking distance45 m1.5 s at 30 m/s — proportional to speed
Braking distance65.553 mproportional to the SQUARE of speed, which is why the total grows so fast
Deceleration6.8647 m/s²0.7 g
Braking time4.37 splus 1.5 s of reaction
Total time5.87 s
At twice the speed352.21 mbraking distance quadruples while thinking distance only doubles
Speed still carried where a slower vehicle would have stopped57.6 m/sthe vehicle travelling twice as fast is still doing this when the slower one is stationary
On wet asphalt159.72 mµ = 0.4
On packed snow274.44 mµ = 0.2
On ice503.87 mµ = 0.1

The formula

distance = v·t_reaction + v² ÷ 2µg

One term is linear, the other is squared

Stopping distance has two parts that scale differently. Thinking distance is speed times reaction time, so it doubles when speed doubles. Braking distance is v²/2a, so it quadruples. That asymmetry is why the totals grow so alarmingly and why speed limits matter more than they intuitively should.

The consequence worth internalising is the residual-speed figure above. A car travelling at twice the speed does not merely stop later — at the point where the slower car has come to rest, it is still moving quickly, and any impact happens at that speed.

Surface dominates everything. Dry asphalt gives about 0.7, wet 0.4, snow 0.2, ice 0.1 — so an icy road can multiply braking distance sevenfold at unchanged speed. A downhill gradient subtracts from the available deceleration directly, and on a steep enough slope with poor grip the sum goes negative, meaning the vehicle cannot stop at all.

These are idealised figures for a locked-grip stop. Real braking involves weight transfer, ABS cycling and tyres well past their best, so treat them as a floor rather than a prediction.