What is a negative split?
A negative split means running the second half of a race faster than the first. A positive split is the reverse — fast first half, slower second — and even splits means both halves take the same time. The split percentage is how much faster (or slower) the second half is than the first, relative to half your total time — the same as the percentage difference in pace between the halves:
positive result = negative split · negative result = positive split
Why negative splits work
At a steady effort, your body relies on a mix of fat and carbohydrate for fuel. Running the early kilometres even slightly too fast uses carbohydrate much faster and accumulates fatigue that cannot be undone later. Starting a touch conservatively keeps more in reserve for the final third, where races are won and lost.
Many distance-running world records have been set with near-even or slightly negative pacing, typically with the two halves within about 1–2 % of each other. For recreational runners, the most common pacing error by far is the opposite: a fast first half followed by a large slowdown.
Negative split targets for popular goals
| Race & goal | Even halves | 1 % negative | 2 % negative | 3 % negative |
|---|---|---|---|---|
| 5K 25:00 | 12:30 / 12:30 | 12:34 / 12:26 | 12:38 / 12:22 | 12:41 / 12:19 |
| 10K 50:00 | 25:00 / 25:00 | 25:07 / 24:53 | 25:15 / 24:45 | 25:22 / 24:38 |
| 10K 1:00:00 | 30:00 / 30:00 | 30:09 / 29:51 | 30:18 / 29:42 | 30:27 / 29:33 |
| Half 1:45:00 | 52:30 / 52:30 | 52:46 / 52:14 | 53:02 / 51:58 | 53:17 / 51:43 |
| Half 2:00:00 | 1:00:00 / 1:00:00 | 1:00:18 / 59:42 | 1:00:36 / 59:24 | 1:00:54 / 59:06 |
| Marathon 3:30:00 | 1:45:00 / 1:45:00 | 1:45:31 / 1:44:29 | 1:46:03 / 1:43:57 | 1:46:34 / 1:43:26 |
| Marathon 4:00:00 | 2:00:00 / 2:00:00 | 2:00:36 / 1:59:24 | 2:01:12 / 1:58:48 | 2:01:48 / 1:58:12 |
| Marathon 4:30:00 | 2:15:00 / 2:15:00 | 2:15:40 / 2:14:20 | 2:16:21 / 2:13:39 | 2:17:02 / 2:12:58 |
Each cell shows first half / second half. Notice how small the differences are: a 2 % negative split in a 4-hour marathon means reaching halfway only 72 seconds behind even pace.
How to run a negative split
- Pick a realistic goal. Base it on a recent race using the race time predictor.
- Hold back early. Run the first 5 km a few seconds per km slower than average goal pace. It should feel almost too easy.
- Settle at goal pace through the middle of the race, checking splits every 5 km rather than every kilometre.
- Press in the final third. From about two-thirds distance, gradually lift the pace if you feel good.
Print it. Put your negative-split plan on your wrist with the pace band generator — it supports the same 1–3 % strategies.
Analysing your own race
Switch to Analyse my halves and enter the two half times from your results or watch. If your second half was more than about 5 % slower than your first, the start was very likely too fast for your fitness on the day — or conditions such as heat or a hilly second half played a part. Next time, try starting 5–10 seconds per km slower than goal pace.
For full race plans, see the marathon pace calculator and our goal pace charts.
Last reviewed: September 2026 · Health disclaimer