Race Time Predictor
Predict your finish time at other race distances from a recent result using the Riegel formula, from the 5K to the marathon, with pace per mile for each. Example: a 25:00 5K predicts about 52:07 for the 10K, 1:55:00 for the half marathon and 3:59:47 for the marathon.
Show steps
How to use the Race Time Predictor
- Enter the values in the fields.
- Press Calculate to see the result with the steps shown.
Formula and method
Riegel formula: T2 = T1 x (D2 / D1)^1.06, where T1 is the known time at distance D1 and T2 is the predicted time at distance D2.
Equivalent race times (Riegel)
| 5K | 10K | Half marathon | Marathon |
|---|---|---|---|
| 20:00 | 41:42 | 1:32:00 | 3:11:49 |
| 25:00 | 52:07 | 1:55:00 | 3:59:47 |
| 30:00 | 1:02:33 | 2:18:00 | 4:47:44 |
| 35:00 | 1:12:58 | 2:41:00 | 5:35:41 |
What the 1.06 exponent means
Pace slows as races get longer, and Peter Riegel found that time grows with distance to the power of about 1.06 across many distances. Faster or better-endurance runners may slow less.
Making predictions more reliable
Use a recent race run all out on a flat course in decent weather. Longer source races (10K or half) predict the marathon better than a 5K.
Beyond the formula
Weekly mileage, long-run experience and fueling decide marathon results more than any formula.
Frequently asked questions
How do I predict my marathon time from a 5K?
Multiply the 5K time by about 9.6 (the Riegel formula with exponent 1.06), then add a margin if your long runs are short.
What is the Riegel formula?
T2 = T1 x (D2/D1)^1.06.
How accurate are race predictors?
Good for distances close to the source race, optimistic for marathons without long-run training.
Which race gives the best prediction?
A recent, hard 10K or half marathon.
Can I use this for ultra distances?
Not reliably; fatigue slows pace much more beyond the marathon.
What if I am a beginner?
Add a margin for the marathon and rely on training paces.
Sources
- Riegel, P.: Athletic Records and Human Endurance (American Scientist, 1981)
- World Athletics: Scoring tables
Related calculators
Related to This Article
More math articles
- The Ultimate TABE Math Course (+FREE Worksheets & Tests)
- Rhode Island RICAS Grade 7 Math Worksheets: 95 Free Printable Skill PDFs with Keys
- Delaware Algebra 1 Free Worksheets: Printable Algebra 1 Test-Prep Worksheets with Answer Keys
- Decoding Discreteness: A Comprehensive Guide to the Probability Mass Function
- How to Solve Word Problems of Absolute Value and Integers?
- New York Grade 4 Math Worksheets: 43 Topic Links
- Washington SBAC Grade 8 Math Free Worksheets: 72 Free Printable Worksheets with Step-by-Step Keys
- How to Employ Solids of Revolution
- How to Find Similar and Congruent Figures?
- Maine Through Year Grade 7 Math Worksheets: 95 Free Printable Single-Skill PDFs
What people say about "Race Time Predictor: Predict Marathon, Half & 10K Times from Any Race"?
No one replied yet.