Skip to content
ENExplore Calculators

Safe Following Distance Calculator

Work out safe following distance instantly with clear inputs, formula shown and shareable results.

About Safe Following Distance Calculator

The two second rule works at any speed because the gap scales automatically with velocity. Double it in the wet, quadruple or more on ice, and increase it again for a heavy vehicle whose braking distance is far longer than a car's.

Formula

Following distance

distance = speed (m/s) x time gap; two seconds dry, four wet, ten or more on ice

Worked example

With the default values below, Safe Following Distance Calculator returns Safe following distance of 61.11. Change any input above and every figure here is recalculated in your browser.

Inputs used

Speed
110 km/h
Road conditionsone of Dry, Wet, Ice or snow, Fog
Dry
Vehicleone of Car, Van or towing, Heavy goods vehicle
Car

Results

Safe following distance
61.11 m
Time gap to keep
2.00 s
Equivalent car lengths
13.58 lengths
Total stopping distance
94.03 m

Step by step

  1. 1Values used
  2. 2Following distance
  3. 3Safe following distance= 61.11 m
  4. 4Time gap to keep= 2.00 s
  5. 5Equivalent car lengths= 13.58 lengths
  6. 6Total stopping distance= 94.03 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 2 decimal places, 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

Why is a time gap better than a distance?

Because it self-adjusts with speed. Two seconds is 61 m at 110 km/h and 17 m at 30 km/h, both about right.

How do I judge two seconds?

Pick a fixed marker the car ahead passes and count. If you reach it before finishing 'only a fool breaks the two second rule', you are too close.

Related Calculators

Safe Following Distance Calculator | Calcrivo