McMillan Race Time Equivalents
Predict equivalent race times for other distances based on a recent race, using the McMillan exponent (similar to the Riegel formula).
Result
1 mile
6:37
Predicted 1 mile time from your 5.00 km base.
- 1 mile6:37
- 5K22:00
- 10K45:52
- Half Marathon1:41:12
- Marathon3:31:00
Very wide extrapolation — unreliable beyond 2× base distance
Equivalent 1 mile
T₂ = T₁ × (0.322)^1.06.
6:37
Equivalent 5K
T₂ = T₁ × (1.000)^1.06.
22:00
Equivalent 10K
T₂ = T₁ × (2.000)^1.06.
45:52
Equivalent Half Marathon
T₂ = T₁ × (4.220)^1.06.
1:41:12
Equivalent Marathon
T₂ = T₁ × (8.439)^1.06.
3:31:00
Not medical advice — Predictions assume equal training across distances and constant conditions. Real-world marathons commonly come in 2-5% slower than the 5K-extrapolated time because of fueling, pacing, heat, and durability. Subtract one minute per mile from predicted marathon time if long runs are not in your training history.
Step-by-step
- Base: 5.000 km in 1320 s.
- Apply T₂ = T₁ × (D₂ / D₁)^1.06 for each target distance.
- Example marathon: 1320 × (42.195 / 5.000)^1.06 = 3:31:00.
How to use this calculator
- Enter a recent race distance and time.
- Read the predicted equivalents for 1 mile, 5K, 10K, half, and full marathon.
- Use as a target — your actual race may differ ±2-5%.
About this calculator
McMillan's race-equivalent table uses an exponent very close to Riegel's 1.06 to predict equivalent race times across distances. The model assumes "all-else-equal" performance — same fitness, same conditions, same training. Real-world results vary because longer races stress endurance, hydration, and pacing in ways the formula cannot model.
Frequently asked
For distances within 2x of your base race, typically within 2-3%. For going from 5K to a marathon (8x), real times are usually slower than predicted unless you specifically train for the marathon.
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