Question 1

What is the Riegel formula?

Accepted Answer

The Riegel formula (T2 = T1 x (D2/D1)^1.06) was developed by Peter Riegel in 1977. It predicts race times at one distance based on a performance at another distance. The exponent 1.06 accounts for the fact that pace slows as distance increases.

Question 2

How accurate is the Riegel formula?

Accepted Answer

The formula is most accurate when predicting between similar distances (e.g., 10K to half marathon). It tends to be optimistic when predicting much longer races from short ones. For best results, use a recent race result from a distance close to your target.

Question 3

Can I adjust the exponent?

Accepted Answer

Yes, our calculator lets you adjust the exponent. The default 1.06 works well for most runners. Faster/younger runners may use 1.04-1.05, while slower or older runners may find 1.07-1.10 more accurate.

Question 4

Should I use my PR or a recent race time?

Accepted Answer

Use your most recent race time, ideally from the last 2-3 months. An old PR may not reflect your current fitness level. The prediction is only as good as the input.

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