Enter your 5K time to see what it predicts for the half marathon.
Your 5K time is a reliable measure of aerobic capacity. This table shows what that capacity predicts for the half marathon — assuming threshold-specific training and half marathon-appropriate long runs. The physiological distance is bridgeable with the right training additions.
Quick answer: A 22:00 5K runner (RPI 44.5) has equivalent Half Marathon fitness of 1:41:11 (7:43/mi). Range in this table: 16:00 5K → 1:13:18 Half Marathon through 35:00 → 2:40:47.
| 5K Time | RPI | Half Marathon Equivalent | Equiv Pace |
|---|---|---|---|
| 16:00 | 64.6 | 1:13:18 | 5:35/mi(3:28/km) |
| 17:00 | 60.2 | 1:17:55 | 5:57/mi(3:42/km) |
| 18:00 | 56.3 | 1:22:34 | 6:18/mi(3:55/km) |
| 19:00 | 52.9 | 1:27:10 | 6:39/mi(4:08/km) |
| 20:00 | 49.8 | 1:31:50 | 7:00/mi(4:21/km) |
| 21:00 | 47 | 1:36:32 | 7:22/mi(4:35/km) |
| 22:00 | 44.5 | 1:41:11 | 7:43/mi(4:48/km) |
| 24:00 | 40.2 | 1:50:26 | 8:25/mi(5:14/km) |
| 26:00 | 36.6 | 1:59:35 | 9:07/mi(5:40/km) |
| 28:00 | 33.5 | 2:08:53 | 9:50/mi(6:07/km) |
| 30:00 | 30.8 | 2:18:17 | 10:33/mi(6:33/km) |
| 35:00 | 25.6 | 2:40:47 | 12:16/mi(7:37/km) |
Computed via StrideIQ’s RPI equation. Predictions assume distance-specific training is in place.
The 5K → half marathon prediction is accurate when half marathon-specific training is in place: long runs of 12–15 miles and threshold tempo runs (25–35 minutes). Without these, most 5K-trained runners underperform their half marathon equivalent by 5–10 minutes. With them, the typical gap closes to 2–4 minutes.
Add two key elements to 5K training: weekly threshold tempo runs (25–35 minutes at threshold pace) and long runs building to 12–15 miles at easy pace. These develop the sustained effort and aerobic endurance that 5K training alone does not.
A 20:00 5K (RPI 49.8) projects to 1:31:50 half marathon fitness at 7:00/mi. This assumes half-marathon specific preparation is in place.
Reliable when half-specific training exists. The 5K measures aerobic capacity that the half marathon uses — but the half demands sustained effort for 70–120 minutes, which requires specific endurance development beyond what 5K training produces.