GlenCalc

Race time predictor

Enter a recent race (or hard time trial) and the predictions follow for other distances. They assume you train for the new distance.

1.06 is Riegel’s value; endurance specialists may be closer to 1.04.

Your answer

Predicted marathon3:50:01
Predictions
DistanceTimePace
5K23:597:43 /mi
10K50:008:03 /mi
10 miles1:22:488:17 /mi
Half marathon1:50:198:25 /mi
Marathon3:50:018:46 /mi

Worked out in your browser. Nothing you type is sent to a server.

How we worked it out

Updated as you change the numbers.

  1. T₂ = T₁ × (D₂ ÷ D₁)^1.06 (Riegel, 1981).

Method and assumptions

Riegel’s formula fits world-class and recreational results well from about 3.5 minutes to 4 hours. Marathon predictions from short races are often optimistic for runners without the long training runs.

Questions

What marathon time does a 50-minute 10K predict?

About 3:50:01.

Sources

Method and figures checked on . Every worked answer on this page is covered by an automated test. Found a mistake? Tell us.

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