Running splits, explained
A split is simply the time you took for one section of a run, usually each kilometre or mile. Looking at them for thirty seconds after a run tells you more about your pacing than the overall average ever will.
The short version
- A split is the time for one section of a run, usually each kilometre or mile.
- Even or slightly negative splits are the most efficient way to pace a race.
- Fading splits on a flat course usually mean you started too fast.
- Look at the pattern across the run, not one odd GPS kilometre.
Reading your splits
Take a 5 km run in 25:55. The average pace is 5:11 per kilometre, but the splits tell the real story:
| Kilometre | Run A | Run B |
|---|---|---|
| 1 | 4:52 | 5:18 |
| 2 | 5:04 | 5:14 |
| 3 | 5:16 | 5:11 |
| 4 | 5:24 | 5:08 |
| 5 | 5:19 | 5:04 |
Both runs have the same total time. Run A started fast and faded: positive splits. Run B started controlled and finished fastest: negative splits. Run B almost always feels better, and in a race it usually finishes faster too.
Even, negative and positive splits
- Even splits: every kilometre at about the same pace. The most efficient way to run a steady race on a flat course.
- Negative splits: the second half faster than the first. A good habit for long runs and races, because you save energy early when it costs the most.
- Positive splits: the second half slower. Normal on hilly routes or into a headwind, but on a flat course it usually means you started too fast.
Many world records over 5,000 metres and longer have been run with very even or slightly negative splits, which is why coaches keep repeating “start slower than you think”.
Using splits in training
- Easy runs: splits should be steady and relaxed. If they creep faster through the run, that is fine; if every run turns into a race, slow down.
- Tempo runs: aim for even splits at a “comfortably hard” pace you could hold for about an hour.
- Intervals: compare each repeat. If the last one is much slower than the first, the target pace was too ambitious.
- Long runs: try finishing the last few kilometres a little faster than the start.
Why your splits may be off
GPS on a phone or watch is usually accurate to within a few percent, but tall buildings, trees and tunnels can make a single kilometre look too fast or too slow. Hills change effort as well as pace. Look at the pattern over the whole run rather than worrying about one odd split.
Turn splits into race estimates
Once you have a few recent runs at a known effort, you can estimate race times. Formulas such as Peter Riegel’s, which scales a time by distance raised to a power of about 1.06, give a reasonable guess for distances from 5 km to the marathon, provided you have trained for the longer distance.
GPS Running App
Record GPS runs with route, km splits, pace and race estimates, then share a 9-second animated route video, a transparent stats sticker or a caption.
See how Sets & Splits does itQuestions
What is a negative split in running?
Running the second half of a run or race faster than the first half.
Are negative splits better?
For most races and long runs, yes: starting controlled and finishing faster saves energy when it matters and usually gives a faster overall time.
Why is one of my kilometre splits much faster than the others?
Usually a GPS glitch from buildings, trees or a tunnel, or a downhill section. Look at the overall pattern.
General training information, not medical advice. If you have a health condition, an injury or symptoms, talk to a doctor or a qualified professional.