Race splits calculator
A target time in, the exact number your watch should read at every marker out. Print it, or write the halfway and three-quarter splits on your hand. Those are the two that matter.
Average pace
5:00/km
First half
25:00
Second half
25:00
Even pacing: every kilometre at the same effort and the same time on the watch.
Split table
| Km | Split | Elapsed | Pace | vs even |
|---|---|---|---|---|
| 1 | 5:00 | 5:00 | 5:00 | — |
| 2 | 5:00 | 10:00 | 5:00 | — |
| 3 | 5:00 | 15:00 | 5:00 | — |
| 4 | 5:00 | 20:00 | 5:00 | — |
| 5 | 5:00 | 25:00 | 5:00 | — |
| 6 | 5:00 | 30:00 | 5:00 | — |
| 7 | 5:00 | 35:00 | 5:00 | — |
| 8 | 5:00 | 40:00 | 5:00 | — |
| 9 | 5:00 | 45:00 | 5:00 | — |
| 10 | 5:00 | 50:00 | 5:00 | — |
How the split table is built
Even pacing is trivial: total time divided by distance, repeated. The negative and positive tables use one model for both: pace changes linearly with distance covered, from a starting pace to a finishing pace, with the average pinned to your target time so the total always comes out exactly right.
Asking for a negative split of s means the second half's average pace should be s
faster than the first half's. For a linear ramp that works out to a half-amplitude of
d = s × average / (1 − s/2) — so the race starts at average + d and
finishes at average − d. That is why a 1.5% negative split does not just mean
"run the second half 1.5% below average": the two halves move apart around the average, not down
from it.
Which splits to actually memorise
A full table is useful for planning and nearly useless mid-race, when reading and comparing numbers is harder than it sounds. Pick two:
- Halfway. The single most informative checkpoint. If you are more than about 1% ahead of plan here, you are in trouble and do not yet know it.
- Three-quarters. The point where a race is won or lost, and the last moment a correction can still work.
Everything between those is noise from GPS drift and tangents. A watch reading 5.08 km at the 5 km marker is normal and means your watch is measuring the line you actually ran.
Before you trust the target
A split table makes any target look achievable, because the numbers are evenly spaced and each one individually seems fine. Check the target against a recent race first with the race time predictor, and check that the implied pace is one you have held in training. The VDOT calculator will tell you what your current fitness supports.
Common questions
What is a negative split?
Running the second half of a race faster than the first. It is the pacing pattern behind a large share of distance-running world records, because it keeps you from spending energy early at a cost you cannot repay. A negative split of 1 to 2% (the second half that much quicker) is the usual recommendation; anything much larger normally means the first half was too slow rather than the second half being brilliant.
Is an even split or a negative split faster?
For a single best performance they are very close, and both comfortably beat going out too fast. An even split is the simplest to execute and is close to optimal from 1500 m upwards. A slight negative split gives you insurance: if the day is going badly you find out while you still have room to adjust, rather than at 4 km of a 5K.
How much time does going out too fast actually cost?
More than the time you gain. A widely used rule of thumb from marathon field data is that each second run faster than goal pace in the early miles costs roughly two seconds in the closing ones. The mechanism is that above threshold pace you accumulate lactate and deplete glycogen faster than you can clear or replace them, and neither debt is repaid by slowing down later.
Should the first kilometre be slower than the rest?
Usually yes, by a few seconds. The first kilometre includes getting up to speed and getting clear of congestion, and the physiological cost of starting fast is the highest of any part of the race. Most experienced racers deliberately give away two to five seconds in the opening kilometre and take them back by halfway.
Can I print this table?
Yes. Use your browser’s print function and the navigation, footer and any ads are removed automatically, leaving just the split table at a size that fits a wrist band or a race number.