Split Time Calculator

The time taken for one segment of a race, or the cumulative clock time at a marker. This page prints both: each row shows the running clock at that point with the pace for that individual segment in brackets, because those are the two numbers a runner needs at different moments.

Running the second half of a race faster than the first. It is the pacing pattern behind essentially every modern distance world record. The opposite, a positive split, is what happens to most runners who do not plan the opening pace.

Because the metabolic cost of running above sustainable intensity early is repaid later at a much worse rate than it was borrowed. Starting conservatively keeps glycogen use and acidosis in check through the middle of the race and leaves you able to make a decision in the closing stages, which a hard start does not.

No, and this is the single most expensive misconception in distance running. Banking assumes a second saved early is worth a second later. It is not: what you actually accumulate is fatigue at compound interest, and the slowdown it causes exceeds the time gained.

For most races, 1 to 3% is a realistic and well-executed negative split. The 4 and 8% options here are useful for progression training runs, where a large deliberate drift is the point, but attempting an 8% negative split in a race usually means the first half was simply too slow.

Yes, by construction. The drift factors are symmetric about the midpoint of the race and average to exactly 1, so the schedule balances arithmetically rather than being corrected afterwards. The engine prints the residual so you can see it is zero.

Use the markers the course actually has. Road races are usually marked every kilometre or every mile; a track gives you 400 m laps. A schedule with markers you cannot see is not useful during the race.

The marathon is 42,195 m, so a kilometre schedule leaves a 195 m tail. The engine prices that tail at the closing pace, which is what you will actually be running when you reach it, and includes it in the total so the finish time is exact.

No. On hills, pace by effort and let the splits fall where they fall — uphill segments will run slow and downhill ones fast, and the plan should balance across the whole course rather than within each segment. These schedules assume a flat, accurately measured route.

More than the time you took. Going out 3% too fast typically costs considerably more than 3% at the finish, because the resulting slowdown is caused by glycogen depletion and neuromuscular fatigue rather than by choice, and it accelerates over the closing kilometres.

Frequently. For shorter races, and for anyone who finds holding back difficult, an even plan is easier to execute and gives up very little. The difference between an even and a 1% negative split is small; the difference between either and a positive split is large.

Set the segment to 400 m and the distance to the total of the repetition. The lap column then gives you the target for each lap. For rest intervals and repetition structure, a training-load or interval tool is more appropriate.

Because a negative split requires it. On a 4% drift the opening kilometre is run about 2% slower than average and the closing one about 2% faster. If that opening pace feels uncomfortably easy, the plan is working as intended.

The arithmetic is identical for any sport measured in distance and time. The pacing advice is less transferable: drafting dominates road cycling tactics, and swimming splits are affected by turns and by pool length in a way running is not.

The engine builds as many full segments as fit and prices the remainder separately at the closing pace. The total still sums to your target exactly, and the tail is shown explicitly rather than being hidden in a rounding.

On a negative-split plan, yes — but only just. The drift is linear across the race, so the first segment is the slowest by a small margin rather than a jog. A first kilometre dramatically slower than the rest is not a negative split, it is a bad start.

The schedule is only as realistic as the target. It is arithmetic and will happily produce a beautifully paced plan for a time you cannot run. Use a race predictor built from a real result to set the target before you pace it.

In record attempts, almost always, though the negative portion is often small and comes from a fast finish rather than a slow start. In championship racing, tactics dominate and splits can be wildly uneven, because the goal is to win rather than to run a fast time.

A headwind on an out-and-back course is not repaid by the tailwind on the return, because the energy cost of wind resistance rises with the square of relative speed. Plan the into-the-wind section slower in effort terms and do not chase the schedule.

Linearly. Segment i of n is scaled by 1 + p(½ − i/(n−1)), so the pace changes by the same amount between every pair of consecutive segments. That is easier to execute than a step change at halfway and matches how well-paced races actually look.