Enter your Marathon time to see what it predicts for the half marathon.
The half marathon and marathon share similar physiological demands — both require sustained aerobic and threshold endurance. This table shows what your marathon fitness predicts for the half marathon. For runners transitioning from marathon to half-marathon focus, the equivalency is often achievable or exceeded within a few weeks.
Quick answer: A 4:00:00 Marathon runner (RPI 37.9) has equivalent Half Marathon fitness of 1:56:07 (8:51/mi). Range in this table: 2:30:00 Marathon → 1:11:40 Half Marathon through 5:30:00 → 2:41:52.
| Marathon Time | RPI | Half Marathon Equivalent | Equiv Pace |
|---|---|---|---|
| 2:30:00 | 66.3 | 1:11:40 | 5:28/mi(3:24/km) |
| 2:45:00 | 59.3 | 1:18:57 | 6:01/mi(3:44/km) |
| 3:00:00 | 53.5 | 1:26:19 | 6:35/mi(4:05/km) |
| 3:15:00 | 48.7 | 1:33:38 | 7:09/mi(4:27/km) |
| 3:30:00 | 44.6 | 1:41:01 | 7:42/mi(4:47/km) |
| 3:45:00 | 41 | 1:48:35 | 8:17/mi(5:09/km) |
| 4:00:00 | 37.9 | 1:56:07 | 8:51/mi(5:30/km) |
| 4:15:00 | 35.2 | 2:03:36 | 9:26/mi(5:52/km) |
| 4:30:00 | 32.8 | 2:11:11 | 10:00/mi(6:13/km) |
| 4:45:00 | 30.6 | 2:18:58 | 10:36/mi(6:35/km) |
| 5:00:00 | 28.7 | 2:26:30 | 11:11/mi(6:57/km) |
| 5:30:00 | 25.4 | 2:41:52 | 12:21/mi(7:40/km) |
Computed via StrideIQ’s RPI equation. Predictions assume distance-specific training is in place.
Marathon → half marathon is among the more reliable reverse-direction predictions. Both distances tax similar energy systems. Marathon-trained runners often slightly outperform their half marathon equivalent because the high-threshold intensity of the half marathon is easier to sustain than marathon pace over 13.1 miles with full marathon training. Typical accuracy: within 2–4 minutes.
Yes — marathon training builds the aerobic base and threshold stamina that the half marathon demands. Marathon runners transitioning to the half often find their performance exceeds the prediction because the shorter distance demands less endurance but similar aerobic and threshold capacity.
A 3:00:00 marathon (RPI 53.5) projects to 1:26:19 half marathon fitness at 6:35/mi.
A 4:00:00 marathon (RPI 37.9) projects to 1:56:07 half marathon potential.