A longer race in. Your 5K out.
Type a recent longer race result. We project your 5K finish using the Riegel formula. Reverse-prediction: longer races slightly overestimate 5K speed.
From 10K in 50:00, here are your projected race times.
Find Marathon races →Reference table — popular race times and the Riegel-projected 5K. Predicting 5K from a marathon is rough; from 10K is reasonable.
| Input race result | Predicted | Notes |
|---|---|---|
| 10K 40:00 | 5K ~19:18 | Sub-20 target. |
| 10K 50:00 | 5K ~24:09 | Solid sub-25. |
| Half 1:30:00 | 5K ~19:21 | Sub-20 territory. |
| Half 1:45:00 | 5K ~22:35 | Sub-23 base. |
| Marathon 4:00:00 | 5K ~24:50 | Caveat: long-to-short prediction is rough. |