Enter your 10K time to see what it predicts for the half marathon.
The 10K and half marathon are the most physiologically similar standard race distances — both demand sustained effort near the lactate threshold for 30–90 minutes. This makes the 10K → half marathon equivalency the most reliable cross-distance prediction available. The table below shows predicted half marathon times for a range of 10K inputs, all computed from StrideIQ’s RPI equation.
Quick answer: A 48:00 10K runner (RPI 42) has equivalent Half Marathon fitness of 1:46:22 (8:07/mi). Range in this table: 32:00 10K → 1:10:33 Half Marathon through 70:00 → 2:35:01.
| 10K Time | RPI | Half Marathon Equivalent | Equiv Pace |
|---|---|---|---|
| 32:00 | 67.5 | 1:10:33 | 5:23/mi(3:21/km) |
| 35:00 | 60.7 | 1:17:21 | 5:54/mi(3:40/km) |
| 38:00 | 55.2 | 1:24:01 | 6:25/mi(3:59/km) |
| 40:00 | 51.9 | 1:28:37 | 6:46/mi(4:12/km) |
| 42:00 | 49.1 | 1:32:58 | 7:05/mi(4:24/km) |
| 45:00 | 45.3 | 1:39:40 | 7:36/mi(4:43/km) |
| 48:00 | 42 | 1:46:22 | 8:07/mi(5:03/km) |
| 50:00 | 40 | 1:50:53 | 8:27/mi(5:15/km) |
| 55:00 | 35.8 | 2:01:53 | 9:18/mi(5:47/km) |
| 60:00 | 32.3 | 2:12:54 | 10:08/mi(6:18/km) |
| 65:00 | 29.3 | 2:24:03 | 10:59/mi(6:49/km) |
| 70:00 | 26.8 | 2:35:01 | 11:49/mi(7:21/km) |
Computed via StrideIQ’s RPI equation. Predictions assume distance-specific training is in place.
The 10K → half marathon prediction is the most accurate in the equivalency system. Both distances tax the same aerobic and threshold energy systems. Runners with consistent weekly training at both distances typically match their equivalency within two to four minutes. The main divergence factor: half marathon-specific long runs (12–15 miles) develop pacing stamina that shorter training blocks do not.
Very accurate — this is the most reliable cross-distance pair in running equivalency. The 10K and half marathon both require sustained effort near lactate threshold, so the aerobic capacity measured by the 10K closely predicts half marathon performance. Most consistently trained runners fall within three to five minutes of their prediction.
A 45:00 10K gives an RPI of 45.3. The equivalent half marathon is 1:39:40 at 7:36/mi. This assumes comparable half marathon preparation.
A 40:00 10K runner (RPI 51.9) has the aerobic capacity for a 1:28:37 half marathon at 6:46/mi. Half marathon pace runs about 10–15 seconds per mile slower than 10K race pace.