Pace, time and distance
Time = Pace × Distance
Distance = Time ÷ Pace
- Pace
- Minutes per kilometre or mile
- Time
- Total elapsed time
- Distance
- Total distance covered
Pace and speed describe the same thing inverted. Pace is time per unit distance — the runner's unit, because it maps directly onto what a watch shows. Speed is distance per unit time, which is what cyclists and treadmills use.
Predicting other distances
A time at one distance predicts times at others, but not by simple scaling — you cannot hold 5K pace for a marathon. The standard model is Pete Riegel's 1977 formula:
- T₁
- Your known time
- D₁
- The distance you ran it over
- D₂
- The distance you want to predict
- 1.06
- The fatigue exponent
The 1.06 exponent captures the fact that pace degrades as distance grows. It is reasonably accurate between 3 km and the marathon for a trained runner, and increasingly optimistic beyond that.
| Distance | Predicted time | Pace per km |
|---|---|---|
| 5 km | 23:59 | 4:48 |
| 10 km | 50:00 | 5:00 |
| Half marathon | 1:50:19 | 5:14 |
| Marathon | 3:50:01 | 5:27 |
Training paces
Most runners run their easy days too fast and their hard days too slow. The classic prescription is roughly 80% of weekly volume at genuinely easy effort.
| Type | Relative pace | Purpose |
|---|---|---|
| Recovery | +90 to +120 sec/km | Active recovery between hard sessions |
| Easy / aerobic | +60 to +90 sec/km | Builds the aerobic base — most of your running |
| Marathon pace | +20 to +30 sec/km | Race-specific endurance |
| Threshold / tempo | +10 to +15 sec/km | Raises the lactate threshold |
| Interval / VO₂max | −10 to −15 sec/km | Maximal aerobic power |
| Repetition | −25 to −35 sec/km | Speed and running economy |
A practical test for easy pace: you should be able to hold a full conversation. If you cannot speak in complete sentences, you are running your easy days too hard.
Frequently asked questions
How do I calculate my running pace?
Divide your total time by the distance. A 50-minute 10K is 50 ÷ 10 = 5:00 per kilometre.
To convert to miles, multiply the per-km pace by 1.60934. A 5:00/km pace is 8:03 per mile.
What is a good running pace?
It depends entirely on experience, age and distance. As a broad reference, a 30-minute 5K (6:00/km) is a common recreational benchmark, and a sub-25-minute 5K (5:00/km) puts you comfortably above average for a casual runner.
Compare yourself against your own previous times rather than anyone else's.
How accurate are race time predictions?
Riegel's formula is reasonably accurate between 3 km and the half marathon for a trained runner. It tends to be optimistic for the marathon, because that distance depends on endurance base and fuelling as much as on speed.
If you have not done the long runs, subtract several minutes from any marathon prediction.
Should I run at a constant pace or negative split?
A negative split — running the second half slightly faster — produces better results for most runners and most distances. It is how nearly every distance world record has been set.
The common error is starting too fast on adrenaline, then fading. Aim for the first kilometre to feel almost too easy.