Whether you're targeting a sub-30 minute 5K, pacing your first marathon, or calculating whether you can complete a trail run before dark, running pace arithmetic is a skill every runner needs. This guide covers all three variables, pace conversions, training zones, and race time prediction.
The Three Running Formulas
Pace (min/km) = Time (minutes) ÷ Distance (km)
Time = Pace × Distance
Distance = Time ÷ Pace
Example: 10 km in 55:00 → Pace = 55 ÷ 10 = 5:30 min/km
Pace Conversion: min/km ↔ min/mile ↔ km/h
| min/km | min/mile | km/h | Equivalent 5K time |
|---|---|---|---|
| 4:00 | 6:26 | 15.0 | 20:00 |
| 4:30 | 7:14 | 13.3 | 22:30 |
| 5:00 | 8:03 | 12.0 | 25:00 |
| 5:30 | 8:51 | 10.9 | 27:30 |
| 6:00 | 9:39 | 10.0 | 30:00 |
| 6:30 | 10:28 | 9.2 | 32:30 |
| 7:00 | 11:16 | 8.6 | 35:00 |
To convert min/km to min/mile: multiply by 1.6093. To convert min/mile to min/km: divide by 1.6093.
Race Finish Time from Pace
| Pace | 5K | 10K | Half marathon | Marathon |
|---|---|---|---|---|
| 4:30/km | 22:30 | 45:00 | 1:35:05 | 3:10:10 |
| 5:00/km | 25:00 | 50:00 | 1:45:40 | 3:31:20 |
| 5:30/km | 27:30 | 55:00 | 1:56:14 | 3:52:28 |
| 6:00/km | 30:00 | 1:00:00 | 2:06:49 | 4:13:38 |
| 6:30/km | 32:30 | 1:05:00 | 2:17:24 | 4:34:48 |
| 7:00/km | 35:00 | 1:10:00 | 2:27:58 | 4:55:57 |
Training Paces by Heart Rate Zone
Running at the right pace for each training session is more important than running fast. Most elite training programmes use 80% of miles at easy/recovery pace and only 20% at threshold or faster (the "80/20 rule").
| Zone | Effort | Pace relative to 5K race pace | Purpose |
|---|---|---|---|
| Zone 1–2 (Easy) | Conversational | Race pace +90 to +120 sec/km | Recovery, aerobic base |
| Zone 3 (Tempo) | Comfortably hard | Race pace +15 to +30 sec/km | Lactate threshold |
| Zone 4 (Threshold) | Hard, 10K effort | Race pace ±10 sec/km | Speed endurance |
| Zone 5 (VO2 max) | Very hard, 1–2 min repeats | Race pace −5 to −15 sec/km | Aerobic capacity |
Predicting Your Marathon from 5K or 10K
Common race prediction formula (Riegel's formula):
T₂ = T₁ × (D₂ ÷ D₁)^1.06
Where T = time, D = distance. The 1.06 exponent accounts for fatigue factor.
Example: 5K in 25:00 → Marathon prediction: 25 × (42.195 ÷ 5)^1.06 = 25 × 8.438^1.06 ≈ 25 × 9.27 ≈ 231 minutes = 3:51:00
Note: race predictions become less accurate over longer distances — the marathon involves nutrition, hydration, and mental factors that short-race performance doesn't predict. Use predictions as a starting point, not a guarantee.