See how far a vehicle travels before it stops, split into reaction distance and braking distance. Enter a speed, a reaction time and a braking deceleration, and optionally a second speed to compare. The calculator shows the distance covered while you react, the distance covered while braking, the total, and how fast the distance grows as speed rises.
You supply every figure. This tool does not suggest a reaction time or a braking figure, and it gives no advice on safe distances or speed limits.
Enter your own figures. This tool does not suggest a reaction time or a braking figure, and it gives no advice on safe distances or speed limits.
Nothing you type is stored or sent anywhere. Results are calculated from the numbers you enter.
How to use the stopping distance calculator
- Enter the speed in km/h.
- Enter a reaction time in seconds. This is the time between seeing a hazard and starting to brake.
- Enter a braking deceleration in m/s², which is how quickly the vehicle slows once the brakes are on. Use a figure from a source you trust, such as a test report for your vehicle.
- Optionally enter a second speed to see how the distance changes.
- Press “Calculate stopping distance”.
How the results are worked out
- Speed in m/s = speed in km/h ÷ 3.6
- Reaction distance = speed in m/s × reaction time in seconds
- Braking distance = (speed in m/s)² ÷ (2 × braking deceleration)
- Total stopping distance = reaction distance + braking distance
Because speed is squared in the braking formula, doubling the speed makes the braking distance four times as long, while the reaction distance only doubles.
Worked example (made-up numbers, not a recommendation)
Take a reaction time of 1.5 seconds and a braking deceleration of 5 m/s².
- At 60 km/h: the reaction distance is 25.0 m, the braking distance is about 27.8 m and the total is about 52.8 m.
- At 120 km/h: the reaction distance is 50.0 m, the braking distance is about 111.1 m and the total is about 161.1 m, around 3.05 times as far.
These numbers only show how the calculation works. They are not typical values for any driver or vehicle.
What this calculator does not include
- Road surface and weather. Wet, muddy, sandy or icy roads can make braking much weaker than a figure measured on a dry road.
- The condition of tyres, brakes and suspension, the load being carried, and the slope of the road.
- Tiredness, distraction, and anything else that makes a driver slower to react.
- Speed limits, safe-gap rules or any other law or advice. We have not verified such figures for this page, so it shows none. Follow the limits and signs on the road.
More tools and guides for drivers
Know the signs you will meet on the road in our Pakistan road signs guide. Keep your vehicle ready with the vehicle service reminder calculator, check tyre changes with the tyre size calculator and keep your licence valid with the driving licence expiry date calculator.
Stopping distance calculator FAQs
What is stopping distance?
It is the total distance a vehicle travels from the moment the driver sees a hazard until it stops. It is the distance covered while reacting plus the distance covered while braking.
What reaction time and braking figure should I use?
That depends on the driver, the vehicle and the road, and this tool does not suggest a value. Use figures from a source you trust and try different ones to see how the result changes.
Why does speed matter so much?
The braking distance grows with the square of the speed, so a small rise in speed adds a lot of distance. The comparison box shows this for two speeds.
Is this the distance I should keep from the vehicle in front?
No. This tool does not give safe-distance advice. It is a simple model, and real stopping distances are usually longer.
Is my data stored?
No. The calculation runs in your browser, and nothing you enter is sent to our servers.