Stopping Distance Calculator
Enter your speed, the road condition and an honest reaction time. The calculator splits stopping into reaction distance - travelled before your foot moves - and braking distance from the friction physics, in metres and car lengths.
Driving-school charts quote one dry number and one wet number. This one shows the arithmetic live: braking grows with the square of speed, ice multiplies it eightfold, and the reaction half is the part your phone stretches.
How to use
- Enter the speed you actually travel, not the limit.
- Pick the honest road condition - wet means properly wet, not freshly damp.
- Set reaction time: 1.5 s is the standard alert driver; tired or distracted adds a full second you cannot brake away.
Frequently asked questions
What is the stopping distance at 100 km/h?
On dry asphalt with a 1.5 s reaction: about 40 m of reaction plus 50 m of braking - roughly 90 metres, twenty car lengths. The same speed on ice stops in around 340 metres, three football pitches.
Why does braking distance grow with the square of speed?
Kinetic energy rises with velocity squared, and every metre of braking must burn it: double from 50 to 100 km/h and the braking part quadruples. The speedometer lies by understatement - the physics is exponential-feeling.
How much does ice increase stopping distance?
Roughly eight times versus dry road, because grip falls from a friction factor near 0.8 to about 0.1. Snow sits between at 0.2 - five times dry. Wet compacts the margin before the cold seasons even arrive.
Does ABS make stopping distances shorter?
Only marginally on dry roads - ABS's gift is steerability while braking, not shorter stops. Shorter stops come from good tyres at correct pressure, honest speeds and an unoccupied reaction window.