Stopping Distance
Estimate total stopping distance including driver reaction time.
About Stopping Distance
Before the brakes engage, the car travels at its original speed for the reaction time. Braking distance then scales with the square of speed divided by grip. Because speed enters squared, a small speed rise produces a much longer stop, which is the core physics argument for slower driving.
Formula
Stopping Distance
Total = v x reaction time + v^2 / (2 x friction x 32.174)
- friction
- Tire-road friction coefficient, lower in rain
Worked example
With the default values below, Stopping Distance returns Reaction Distance of 88. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Speedminimum 0 mph
- 60 mph
- Reaction timeaccepts 0–3 s
- 1 s
- Tire frictionaccepts 0.1–1
- 0.7
Results
- Reaction Distance
- 88 ft
- Braking Distance
- 172 ft
- Total Stopping Distance
- 260 ft
- Total in Meters
- 79 m
Step by step
- 1Values used
- 2Stopping Distance
- 3Reaction Distance= 88 ft
- 4Braking Distance= 172 ft
- 5Total Stopping Distance= 260 ft
- 6Total in Meters= 79 m
Assumptions and limits
- The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
- Figures are rounded for display to whole numbers, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is Stopping Distance calculated?
Total = v x reaction time + v^2 / (2 x friction x 32.174) Before the brakes engage, the car travels at its original speed for the reaction time. Braking distance then scales with the square of speed divided by grip.
Why does Stopping Distance matter?
Because speed enters squared, a small speed rise produces a much longer stop, which is the core physics argument for slower driving.
What values do I need to enter?
This calculator takes 3 inputs: Speed, Reaction time, Tire friction. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.