How to use the Running Pace
- Enter any two of pace, distance and time to solve for the third.
- Use a recent race result rather than a training run for predictions.
- Check the predicted times at other distances for consistency.
- Convert between minutes per mile and per kilometre as needed.
How the calculation works
Pace is time divided by distance, and finish time is pace times distance — straightforward arithmetic, complicated only by sexagesimal time. Race prediction uses Riegel's formula, T₂ = T₁ × (D₂ ÷ D₁)^1.06, where the exponent above one captures the fact that pace necessarily slows as distance grows.
Riegel's prediction holds well for doubling distance in a trained runner but overestimates for anyone stepping far beyond their trained range, particularly into the marathon, where glycogen depletion and muscular damage impose limits the formula does not model. A 10K time predicts a half marathon reliably; predicting a marathon from a 5K without marathon-specific long runs will produce a time you cannot hold. Pacing evenly, or very slightly negative, produces the best results in practice — nearly all marathon blow-ups originate in the first ten kilometres.
Pace = time / distance ; Riegel: T₂ = T₁ × (D₂ / D₁)^1.06 ; 1 mile = 1.609344 kmSource: Peter Riegel's endurance time prediction formula (1977), widely used exponent 1.06.
Worked example
A 10K in 47:20, predicting the half marathon and marathon.
- Pace = 2,840 s / 10 km = 4:44 per km.
- Half: 2,840 × (21.0975/10)^1.06 = 2,840 × 2.2318 = 6,338 s = 1:45:38.
- Marathon: 2,840 × (42.195/10)^1.06 = 2,840 × 4.6555 = 13,222 s = 3:40:22.
About 1:45:38 for the half and 3:40:22 for the marathon — the half is realistic, the marathon only with dedicated long-run training.
Frequently asked questions
How accurate are equivalent race predictions?+
Good within a doubling of distance for a trained runner. Marathon predictions from short races run optimistic because endurance-specific training matters more than raw speed at that distance.
Should I run even splits?+
Even or very slightly negative splits produce the best results. Going out fast feels sustainable early and costs far more in the closing miles than it gained.
How do I convert pace between miles and kilometres?+
Multiply minutes per kilometre by 1.609 to get minutes per mile, or divide the other way. A 5:00/km pace is about 8:03 per mile.
Why is my race pace faster than training pace?+
Taper, adrenaline, competition and fresh legs all contribute. Most training should be considerably slower than race pace to build aerobic base without accumulating fatigue.
Last reviewed August 31, 2026. We review this page whenever the underlying formula, tax year, published rate or standard changes.