Work out your pace per km or mile from distance and time.
Pace is time per unit distance — minutes per kilometre or per mile. Speed is distance per unit time. Runners think in pace because it is what a watch displays and what you hold during a race; cyclists think in speed.
Pace = time ÷ distance · Speed = distance ÷ time
To convert between metric and imperial pace, multiply minutes per kilometre by 1.609. A 5:00/km pace is roughly 8:03/mile. A useful anchor: 6:00/km is about 10 km/h, which makes mental arithmetic easy.
| Pace /km | 5K | 10K | Half | Marathon |
|---|---|---|---|---|
| 4:00 | 20:00 | 40:00 | 1:24:24 | 2:48:48 |
| 5:00 | 25:00 | 50:00 | 1:45:30 | 3:31:00 |
| 6:00 | 30:00 | 1:00:00 | 2:06:36 | 4:13:12 |
| 7:00 | 35:00 | 1:10:00 | 2:27:42 | 4:55:24 |
These assume even splits. In practice, most runners lose time in the second half of a marathon, so a marathon time predicted directly from a 10K pace is usually optimistic by several minutes.
A widely used guideline is that around 80 percent of training volume should be easy — comfortable enough to hold a conversation, typically 60 to 90 seconds per kilometre slower than 10K race pace. The remaining 20 percent covers threshold, interval, and race-pace work.
The most common training error is running easy days too hard, which accumulates fatigue without the adaptation benefit of genuinely hard sessions. Running slower on easy days usually allows the hard days to be harder, which is where most of the improvement comes from.
Negative splitting — running the second half slightly faster than the first — produces better outcomes for most runners than going out fast. Starting 5 to 10 seconds per kilometre slower than target for the first few kilometres costs very little and protects against a much larger late-race collapse.