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Marathon Finish Prediction Calculator

Work out marathon finish prediction instantly with clear inputs, formula shown and shareable results.

About Marathon Finish Prediction Calculator

This is Riegel's formula, t2 = t1 x (d2 / d1) ^ 1.06, where the exponent above one encodes the fact that pace inevitably drops as distance grows. Riegel is accurate within a few percent for distances within about a factor of four, but it assumes marathon-specific endurance you may not yet have trained.

Formulas

Riegel prediction

t2 = t1 x (d2 / d1) ^ 1.06

Required pace

pace = predicted time / target distance

Worked example

With the default values below, Marathon Finish Prediction Calculator returns Predicted finishing time of 207.01. Change any input above and every figure here is recalculated in your browser.

Inputs used

Distance you have racedminimum 0.1 km
10 km
Time for that distanceminimum 0.1 min
45 min
Target race distanceminimum 0.1 km
42.195 km

Results

Predicted finishing time
207.01 min
Predicted time in hours, minutes and seconds
3:27:01
Required average pace
4:54
Pace slowdown versus the known race
9.02%

Step by step

  1. 1Values used
  2. 2Riegel prediction
  3. 3Required pace
  4. 4Predicted finishing time= 207.01 min
  5. 5Predicted time in hours, minutes and seconds= 3:27:01
  6. 6Required average pace= 4:54
  7. 7Pace slowdown versus the known race= 9.02

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

How is the Marathon Finish Prediction figure worked out?

t2 = t1 x (d2 / d1) ^ 1.06. This is Riegel's formula, t2 = t1 x (d2 / d1) ^ 1.06, where the exponent above one encodes the fact that pace inevitably drops as distance grows.

Why does this matter?

Riegel is accurate within a few percent for distances within about a factor of four, but it assumes marathon-specific endurance you may not yet have trained.

What do I need to enter?

Enter distance you have raced, time for that distance, target race distance. The defaults shown are a realistic worked example — swap in your own figures to get a result you can use.

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