Marathon to 5K Race Equivalency
Your marathon time reflects deep aerobic fitness built from high mileage and sustained endurance training. This table shows what that aerobic capacity predicts for the 5K — a very different kind of race. The 5K demands raw speed and VO2max output that marathon training may not fully develop.
Quick answer: A 4:00:00 Marathon runner (RPI 37.9) has equivalent 5K fitness of 25:14 (8:07/mi). Range in this table: 2:30:00 Marathon → 15:39 5K through 5:30:00 → 35:11.
Marathon → 5K Equivalency Table
| Marathon Time | RPI | 5K Equivalent | Equiv Pace |
|---|---|---|---|
| 2:30:00 | 66.3 | 15:39 | 5:02/mi(3:08/km) |
| 2:45:00 | 59.3 | 17:13 | 5:32/mi(3:26/km) |
| 3:00:00 | 53.5 | 18:49 | 6:03/mi(3:46/km) |
| 3:15:00 | 48.7 | 20:23 | 6:34/mi(4:05/km) |
| 3:30:00 | 44.6 | 21:58 | 7:04/mi(4:23/km) |
| 3:45:00 | 41 | 23:36 | 7:36/mi(4:43/km) |
| 4:00:00 | 37.9 | 25:14 | 8:07/mi(5:03/km) |
| 4:15:00 | 35.2 | 26:51 | 8:39/mi(5:22/km) |
| 4:30:00 | 32.8 | 28:29 | 9:10/mi(5:42/km) |
| 4:45:00 | 30.6 | 30:10 | 9:43/mi(6:02/km) |
| 5:00:00 | 28.7 | 31:49 | 10:14/mi(6:22/km) |
| 5:30:00 | 25.4 | 35:11 | 11:19/mi(7:02/km) |
Computed via Daniels/Gilbert oxygen cost equation (1979). Predictions assume distance-specific training is in place.
How accurate is this prediction?
Marathon → 5K predictions often show that marathon-trained runners underperform their 5K equivalent. Marathon training builds endurance and fat metabolism; the 5K demands high-intensity VO2max output that requires specific interval training. Most marathon runners find their actual 5K runs 30–90 seconds per mile slower than race pace implies — their aerobic engine is there but the high-speed neuromuscular and metabolic systems need 5K-specific training.
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
Why do marathon runners often underperform their 5K equivalent?
Marathon training develops aerobic endurance and fat-based fuel economy. The 5K requires running at near-maximum aerobic output for 15–35 minutes — a VO2max-demanding effort that marathon training does not specifically develop. Adding interval training (800m–1200m repeats at interval pace) bridges this gap for marathon runners wanting to run fast 5Ks.
What 5K does a 3:00:00 marathon predict?
A 3:00:00 marathon (RPI 53.5) projects to 18:49 5K fitness at 6:03/mi. Marathon runners may need 6–12 weeks of 5K-specific interval training to realize this potential.
What 5K does a 4:00:00 marathon predict?
A 4:00:00 marathon (RPI 37.9) projects to 25:14 5K fitness.