25-minute 5K
Average: 5:00/km · 8:03/mile · halfway 12:30.
Checkpoints: 1 mile 8:03 · 5K 25:00.
A 2% negative split gives about 12:38 / 12:22, moving from 5:03/km to 4:57/km.
Race Split Calculator for 5K, 10K, Half Marathon and Marathon
Turn a target finish time or running pace into cumulative mile, kilometre and key-checkpoint targets for an even or negative-split race plan. Use it as a race split planner, track-workout calculator or printable pace band.
Build your race plan
How to use
- Choose a race and calculate from a finish time or pace.
- Select checkpoint spacing, then choose even pacing or a gentle 1–3% negative split.
- Use cumulative course targets, copy a pace band, or export the full plan.
Race split plan
Your 5K plan will appear below.
Distance: —
Finish: —
Official avg pace: —
GPS-watch pace: —
Flat-equivalent pace: —
Allowances: —
Half targets: —
Half paces: —
Pace difference: —
| Checkpoint | Target | Pace / km | Pace / mile |
|---|---|---|---|
| Enter valid settings to calculate. | |||
Race-day pace band
Calculate a plan to create a wrist strip.
Full split table
| Marker | Lap time | Segment pace | Cumulative |
|---|---|---|---|
| Enter valid settings to calculate. | |||
| Finish target: — | |||
Official targets use certified course distance. Watch pace accounts for expected extra recorded distance. A segment crossing halfway uses its actual blended time and pace.
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Worked running split examples
50-minute 10K
Average: 5:00/km · 8:03/mile · halfway 25:00.
Checkpoints: 1 mile 8:03 · 5K 25:00 · 10K 50:00.
A 2% negative split gives about 25:15 / 24:45.
1:45 half marathon
Average: 4:59/km · 8:01/mile · halfway 52:30.
Checkpoints: 5K 24:53 · 10K 49:46 · finish 1:45:00.
A 2% negative split gives about 53:02 / 51:58.
4-hour marathon
Average: 5:41/km · 9:09/mile · halfway 2:00:00.
Checkpoints: 10K 56:53 · 20 miles 3:03:07 · 40K 3:47:31 · finish 4:00:00.
A 2% negative split gives about 2:01:13 / 1:58:47.
Choosing and adjusting a race-split strategy
Even pacing is a strong baseline; a gentle negative split asks you to start slightly slower and finish slightly faster. Taken together, current research suggests—not proves—that no one plan fits every runner: a 2024 systematic review found marathon pacing is dynamic and influenced by ability and other factors, while observational work associates steadier pacing with stronger performances. Use 1–3% only when it matches training, recent race evidence and the course. Sources: 2024 systematic review of marathon pacing and New York City Marathon pacing study.
By race distance
- 5K: avoid a first-kilometre surge; small pace changes matter quickly.
- 10K: settle early, reassess near halfway, and save the strongest change for late.
- Half marathon: even effort is usually more practical than forcing identical clock pace over hills.
- Marathon and 50K: use a conservative goal supported by long-run preparation; late slowing is common in race data.
Conditions and course
- Hills: hold sustainable effort uphill and recover speed gradually downhill instead of chasing every flat-course split.
- Heat and wind: lower the pace target when conditions make the planned effort unsustainable.
- Aid stations: add expected stopped time so the finish target remains honest.
- GPS and tangents: official courses are measured along the shortest permitted route, so weaving and wide turns can make a watch record farther. Source: World Athletics Road Running Manual.
Formulas, assumptions and verification
Pace is time divided by distance. Segment time is cumulative time at the segment end minus cumulative time at its start. Miles convert using 1 mile = 1.609344 km. A half marathon is exactly 21.0975 km; a marathon is exactly 42.195 km.
official course pace = moving time ÷ official distance
GPS-watch pace = moving time ÷ expected recorded distance
second-half pace = first-half pace × (1 − improvement)
first-half time = moving time ÷ (2 − improvement)
second-half time = moving time − first-half time
cumulative time = integrated segment pace + proportional allowances
GPS-watch pace = moving time ÷ expected recorded distance
second-half pace = first-half pace × (1 − improvement)
first-half time = moving time ÷ (2 − improvement)
second-half time = moving time − first-half time
cumulative time = integrated segment pace + proportional allowances
With an abrupt change, those two paces meet at halfway. With a progressive change, pace changes linearly across distance while preserving the same average first- and second-half paces. A row that crosses halfway is calculated from its start and end times, so it shows a blended pace. Values are calculated at full precision and rounded to the nearest second only for display; the final partial mile or kilometre is shorter than a full segment.
Reviewed by: Starlight Tools editorial teamLast reviewed: Processing: entirely in this browser
Assumptions and limits
The calculator assumes one chosen pace model, distributes stop and course allowances proportionally, and does not model elevation, wind, heat, surface, fatigue or the exact location of stops. Course-profile percentages are user-facing estimates, not performance predictions. GPS distance is only an estimate. This is planning mathematics, not coaching or medical advice.
Verified test cases
- 5K in 25:00 at even pace: five 5:00 kilometres total exactly 25:00 before display rounding.
- 10K in 50:00 with a 2% negative split: calculated halves total exactly 50:00.
- Marathon in 4:00:00: all full kilometres plus the final 0.195 km total exactly 4:00:00 before row display rounding.
Race split calculator FAQ
What are race splits?
Race splits divide a race into distances such as kilometres, miles or laps. A split plan gives the time for each segment and the cumulative clock time you should see at each marker.
What is the difference between lap time and cumulative time?
Lap or segment time is the time spent since the previous marker. Cumulative time is total elapsed time from the start and is usually the easier value to check against an official course clock.
How is negative-split percentage defined here?
A 2% improvement means the second-half pace in seconds per kilometre or mile is exactly 2% lower, and therefore faster, than the first-half pace. It does not mean a 52/48 division of total race time.
Is even pacing or negative-split pacing better?
Even pacing is the simplest baseline. A gentle negative split can suit a runner whose goal and fitness support a controlled start, but neither strategy guarantees a result and hills, weather and fatigue can require adjustment.
Why does a marathon have a final partial mile or kilometre?
A marathon is exactly 42.195 kilometres, which is about 26.219 miles. The last row is shorter than a full unit, so its segment time is shorter even though its displayed pace is calculated correctly for that partial distance.
How do hills and GPS affect split targets?
Official markers follow the certified course, while a watch can record extra distance from bends, weaving and GPS error. Hills and weather also change effort. Use the optional allowances as planning estimates, then pace by effort when conditions demand it.
Should I choose kilometre or mile markers?
Choose the markers used by your event when possible. For track workouts choose 400 m or 800 m; for road races use kilometres or miles; and use the key-checkpoint table when you only need the major targets.