What this result means
Negative splitting is a race tactic: run the second half faster than the first. This calculator takes a distance, a target finish, and a percentage (default 2%) and builds checkpoints. The second-half time is that percent less than the first-half time. The two halves still add to the goal clock.
Even-split tables live on the race split calculator. This page exists because even is not the only plan. Many marathoners aim a little slow to halfway, then close.
For 1:45:00 over 21.0975 km with a 2% negative split, the first half takes a little more than half the time and the second half a little less. Kilometre 1 is slower than kilometre 21. The finish is still 1:45:00.
A 4:00:00 marathon with 2% negative puts halfway later than 2:00:00. That is the point: bank a small surplus of energy, not a large surplus of clock. A 5% drop is aggressive for most people.
Calculation method
Let drop be the fraction (2% is 0.02). First-half time is total ÷ (2 − drop). Second-half time is the remainder. Each half uses a constant pace over half the distance. Checkpoints before halfway use the first pace; after halfway they add the second-half pace.
This is exact arithmetic on the profile you typed. It is not a physiology model and not a heat adjustment.
Crowds, hills, and aid stations will not match every row. A large negative split on a hot marathon is often worse than even. Pair this with a pace band if you want km and mile columns on a bib.
Frequently asked questions
What is a negative split?
Running the second half faster than the first. This tool turns that idea into a checkpoint table for a target finish.
What percent should I use?
1–3% is a common planning range. 2% is the default. Bigger drops move more time into the first half and demand a stronger close.
Is this the same as even splits?
No. Even splits keep one pace. Negative splits use a slower first-half pace and a faster second-half pace that still sum to the goal.