Build a per-kilometre or per-mile split table for your goal time — even, negative or positive splits that add up to the finish time exactly. Runs entirely in your browser — your numbers never leave this device.
| Km | Split time | Cumulative time |
|---|---|---|
| 1 | 0:05:06 | 0:05:06 |
| 2 | 0:05:05 | 0:10:11 |
| 3 | 0:05:03 | 0:15:14 |
| 4 | 0:05:02 | 0:20:16 |
| 5 | 0:05:01 | 0:25:17 |
| 6 | 0:04:59 | 0:30:16 |
| 7 | 0:04:58 | 0:35:14 |
| 8 | 0:04:57 | 0:40:11 |
| 9 | 0:04:55 | 0:45:06 |
| 10 | 0:04:54 | 0:50:00 |
Negative and positive plans tilt the pace by 2% either side of the average: the first split runs 2% off the mean pace and each split moves linearly until the last split is 2% the other way. The splits always add up to your goal time exactly.
A split table answers the only pacing question that matters on race day: what should the watch say at each kilometre or mile? This calculator builds the table as an arithmetic progression — a sequence of split times stepping by a constant amount — constrained so the splits sum to your goal time exactly, to the second. Even splits are the degenerate case: every step is zero, each split equals the average pace, and the cumulative column simply counts up by that pace.
Negative and positive splits tilt the progression by 2% either side of the mean pace, the tilt this page defines precisely so the plan is reproducible: for a negative split the first split runs at a pace 2% slower than the mean and each following split is faster by an equal step, until the last split runs 2% faster than the mean; a positive split mirrors it, banking time early and paying it back. Because the progression is symmetric about the mean, the average is untouched and the total is still your goal time exactly. A short final split — the marathon's last 0.195 km, for instance — takes its place in the progression at its own length, and the whole table is rescaled by a hair if that partial length would otherwise move the total off the goal by a fraction of a second.
Which strategy suits you is physiology and temperament, not maths: negative splitting matches how most world records are set, because it respects the cost of early fatigue, while even splitting is simplest to execute on a flat, calm course. Whichever you choose, the average pace is fixed by the goal — check it on the Running Pace Calculator, and sanity-check the goal itself on the Race Time Predictor before committing to the plan.
Running the second half of a race faster than the first. In this calculator's precise version, the first split is run at a pace 2% slower than your average and the last at 2% faster, with a straight-line progression between them — for a 50:00 10K that is a 5:06 opening kilometre easing to a 4:54 closer. Most distance world records are set this way because early restraint protects the finish.
Because 2% either side of the mean is a deliberate, executable race plan rather than a wish. Over a 10K it moves the first split by 6 seconds and the last by 6 the other way — noticeable discipline early, a real lift late. Bigger tilts usually describe what happened in a race that went wrong (or exceptionally right), not a plan a runner can hold across every split.
Yes — that is the construction rule, not a hope. The progression is symmetric about the mean pace, so its average is the mean and the total is the goal. When a partial final split (a marathon's last 0.195 km) would disturb the symmetry, every split is rescaled by goal ÷ raw total so the sum is exact; the test vectors for this tool assert the sum to within a fraction of a second.
Whichever your course marks and your watch displays. Kilometre splits give more frequent, smaller corrections; mile splits mean fewer checks and bigger per-split numbers (the same 50:00 10K is 8:03 per mile). The strategy percentages and the exact total are identical either way — use the toggle to match the markers on your course.
This table distributes effort evenly or in a smooth tilt; it does not model terrain. On a hilly course, treat the cumulative column as your anchor rather than each individual split: let the climbs run slow, take the time back on the descents, and judge yourself at the cumulative checkpoints every few units instead of chasing a flat-course split uphill.
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