Half Marathon to Marathon Race Equivalency
Your half marathon time is the best single predictor of marathon fitness available short of racing a marathon. Both distances demand aerobic and threshold endurance — the half marathon measures these qualities directly. This table shows what your half time predicts for the full 26.2, assuming full marathon preparation.
Quick answer: A 1:45:00 Half Marathon runner (RPI 42.6) has equivalent Marathon fitness of 3:37:56 (8:19/mi). Range in this table: 1:15:00 Half Marathon → 2:36:55 Marathon through 2:30:00 → 5:06:54.
Half Marathon → Marathon Equivalency Table
| Half Marathon Time | RPI | Marathon Equivalent | Equiv Pace |
|---|---|---|---|
| 1:15:00 | 62.9 | 2:36:55 | 5:59/mi(3:43/km) |
| 1:20:00 | 58.4 | 2:47:11 | 6:23/mi(3:58/km) |
| 1:25:00 | 54.5 | 2:57:16 | 6:46/mi(4:12/km) |
| 1:30:00 | 51 | 3:07:30 | 7:09/mi(4:27/km) |
| 1:35:00 | 47.9 | 3:17:41 | 7:32/mi(4:41/km) |
| 1:40:00 | 45.1 | 3:27:51 | 7:56/mi(4:56/km) |
| 1:45:00 | 42.6 | 3:37:56 | 8:19/mi(5:10/km) |
| 1:55:00 | 38.3 | 3:58:00 | 9:05/mi(5:39/km) |
| 2:00:00 | 36.5 | 4:07:29 | 9:26/mi(5:52/km) |
| 2:10:00 | 33.2 | 4:27:15 | 10:12/mi(6:20/km) |
| 2:20:00 | 30.3 | 4:47:31 | 10:58/mi(6:49/km) |
| 2:30:00 | 27.9 | 5:06:54 | 11:42/mi(7:16/km) |
Computed via Daniels/Gilbert oxygen cost equation (1979). Predictions assume distance-specific training is in place.
How accurate is this prediction?
Half marathon → marathon is the most reliable long-distance prediction. Both distances tax similar energy systems, and runners who have built comparable training for each distance typically run within 5–10 minutes of their equivalency. The main divergence: runners who have trained specifically for the half but lack 20-mile long runs underperform their marathon equivalent by 10–20 minutes. Long-run endurance is the variable the half cannot measure.
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
Is half marathon to marathon the most reliable equivalency?
Yes — the half marathon is the best single non-marathon predictor of marathon fitness. Both distances require sustained aerobic and threshold endurance for 70–210+ minutes. The primary gap: the marathon demands specific long-run adaptation (20-mile long runs) that the half marathon does not test.
What marathon does a 1:30:00 half predict?
A 1:30:00 half marathon (RPI 51) projects to a 3:07:30 marathon at 7:09/mi. This assumes full marathon preparation including 20-mile long runs.
What marathon does a 1:45:00 half predict?
A 1:45:00 half marathon (RPI 42.6) projects to 3:37:56 marathon at 8:19/mi.