Marathon to Half Marathon Race Equivalency
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 → Half Marathon Equivalency Table
| 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 Daniels/Gilbert oxygen cost equation (1979). Predictions assume distance-specific training is in place.
How accurate is this prediction?
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.
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
Will marathon training help my half marathon time?
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.
What half marathon does a 3:00:00 marathon predict?
A 3:00:00 marathon (RPI 53.5) projects to 1:26:19 half marathon fitness at 6:35/mi.
What half marathon does a 4:00:00 marathon predict?
A 4:00:00 marathon (RPI 37.9) projects to 1:56:07 half marathon potential.