Negative Split Calculator
Enter a distance, a goal time or pace, and how many seconds per kilometer or mile the second half should be faster. The calculator returns both half paces, both half times, and a complete split table — negative and positive splits are scenarios, not recommendations.
RunPaceKit — runpacekit.com
Split plan — enter your distance, target and half difference to see the plan.
Two-pace model: first-half pace = average + q/2, second-half pace = average − q/2; displayed cumulatives rounded to the second.
Your inputs
Positive = second half faster (negative split). Negative = positive split. Empty means even pacing.
Enter a distance, a goal time or goal pace, and the half difference to build your split table.
These results calculate a pacing scenario from your inputs. They do not predict your fitness or guarantee that a target is achievable.
How the two-pace model works
Your target time sets an average pace. The half difference q shifts pace between the halves symmetrically: first half at average + q/2, second half at average − q/2, so the total is preserved exactly. The difference is capped at 120 seconds per km (about 193 seconds per mile), and both half paces must stay above zero. Where a split interval crosses the halfway point of the race, that row combines both paces, and displayed segment times are differences of rounded cumulative times so they sum exactly to your target.
Worked example
A 10 km race in 50:00 with q = 24 gives a first half at 5:12 per km (26:00) and a second half at 4:48 per km (24:00). The total is still 50:00 — only the distribution changed. Setting q to 0 reproduces the even split table, and a negative q models a positive split.
Frequently asked questions
What is a negative split?
A negative split means the second half of a race is faster than the first half. A positive split is the opposite: the second half is slower. An even split runs both halves at the same pace.
How does the calculator distribute the time?
It uses a two-segment model: with q as your chosen half difference, the first-half pace is the average pace plus q/2 and the second-half pace is the average minus q/2. The total time always equals your target — only the distribution changes. The full derivation is in even vs negative splits.
Are these pacing scenarios recommendations?
No. Even, negative and positive splits are arithmetic scenarios built from your inputs. Whether any of them suits your fitness and the course is a question for you and, where relevant, a coach — the calculator only does the math.
Related guides
- Even vs negative splits — the model, the math, and what changes between the scenarios.
- Planned pace vs actual results — what to do when the race does not follow the plan.