10K to Marathon Race Equivalency
Your 10K time reveals your aerobic capacity and threshold fitness. This table shows what that fitness predicts for the marathon — the equivalent time that the same aerobic engine could support, assuming full marathon-specific preparation. The caveat is always marathon preparation: long runs, glycogen economy, and pacing experience matter enormously.
Quick answer: A 48:00 10K runner (RPI 42) has equivalent Marathon fitness of 3:40:35 (8:25/mi). Range in this table: 32:00 10K → 2:27:44 Marathon through 70:00 → 5:16:41.
10K → Marathon Equivalency Table
| 10K Time | RPI | Marathon Equivalent | Equiv Pace |
|---|---|---|---|
| 32:00 | 67.5 | 2:27:44 | 5:38/mi(3:30/km) |
| 35:00 | 60.7 | 2:41:46 | 6:10/mi(3:50/km) |
| 38:00 | 55.2 | 2:55:22 | 6:41/mi(4:09/km) |
| 40:00 | 51.9 | 3:04:45 | 7:03/mi(4:23/km) |
| 42:00 | 49.1 | 3:13:34 | 7:23/mi(4:35/km) |
| 45:00 | 45.3 | 3:27:07 | 7:54/mi(4:55/km) |
| 48:00 | 42 | 3:40:35 | 8:25/mi(5:14/km) |
| 50:00 | 40 | 3:49:35 | 8:45/mi(5:26/km) |
| 55:00 | 35.8 | 4:11:30 | 9:36/mi(5:58/km) |
| 60:00 | 32.3 | 4:33:14 | 10:25/mi(6:28/km) |
| 65:00 | 29.3 | 4:55:21 | 11:16/mi(7:00/km) |
| 70:00 | 26.8 | 5:16:41 | 12:05/mi(7:30/km) |
Computed via Daniels/Gilbert oxygen cost equation (1979). Predictions assume distance-specific training is in place.
How accurate is this prediction?
The 10K → marathon prediction is accurate for runners with complete marathon training (20-mile long runs, marathon-pace work, 50+ miles/week). Without this preparation, most 10K-trained runners underperform by 15–30 minutes. The 10K is a better aerobic benchmark for marathon than shorter distances — but specific marathon training is the non-negotiable variable.
Equivalency predicts potential — training determines actuals
This table shows what your aerobic capacity predicts at a different distance. StrideIQ tracks whether your training is actually developing the distance-specific fitness needed to meet that potential — long-run adaptation, pacing control, threshold stamina — from your own workout data.
Common questions
How accurate is 10K to marathon prediction?
Accurate for runners with proper marathon preparation. The 10K measures aerobic and threshold fitness that the marathon uses — but the marathon demands glycogen economy and sustained pacing that only long-run training develops. Runners with 20-mile long runs and marathon-pace work typically land within 5–10 minutes of their prediction.
What marathon does a 40:00 10K predict?
A 40:00 10K (RPI 51.9) projects to a 3:04:45 marathon at 7:03/mi. This is the aerobic potential — reaching it requires 20-mile long runs and a full marathon build.
What marathon does a 50:00 10K predict?
A 50:00 10K (RPI 40) projects to 3:49:35 marathon potential at 8:45/mi.