semkuRace pace calculator 5K
Enter a distance and finish time or pace to calculate your splits.
Calculation options
Splits
| Distance from start (km) | Section time (mm:ss or hh:mm:ss) | Time from start (mm:ss or hh:mm:ss) |
|---|---|---|
| 1 km | 05:00 | 05:00 |
| 2 km | 05:00 | 10:00 |
| 3 km | 05:00 | 15:00 |
| 4 km | 05:00 | 20:00 |
| 5 km | 05:00 | 25:00 |
Each time is rounded from its unrounded value, so displayed section times may not add up to the displayed total.
Sources
NIST — SP 811: Guide for the Use of the International System of Units (SI)
Appendix B.8 lists 1 mile = 1.609344 km as an exact conversion. This calculator uses that defined value for km and mi conversions.
Calculation rules
Enter a distance and either a finish time or a pace. The calculator finds the other value and shows pace per km, pace per mile and speed.
This calculator uses preset distances of 5 km for 5K, 10 km for 10K and 42.195 km for the marathon; the half marathon preset is half of 42.195 km, which is 21.0975 km. Times use the same constant pace and do not assess your ability.
Choose km or mi splits. The final partial section is included, with its actual section time. Internal values stay unrounded; each time is rounded to the nearest second, with halfway values rounded up, and speed to two decimal places.
Pace uses separate minutes and seconds fields per selected distance unit. Finish time uses separate hours, minutes and seconds fields. All fields are whole numbers, minutes and seconds range from 0 to 59, and hours start at 0. Total time and pace must be above zero.
The limits of 1,000 km and 1,000 h are calculation limits, not limits on what a person can do. Longer split tables are divided into pages within this page, up to 1,000 km rows or 622 mi rows.
Only distance and time enter the calculation; no adjustments for external conditions or individual differences are applied.
For distance d in km and time t in seconds: pace = t/d in seconds/km; finish = pace × d in seconds; speed = d × 3600/t in km/h. Exactly 1 mi = 1.609344 km. Convert pace to seconds/km before using these formulas. Round displayed times to the nearest second, with positive halfway values rounded up, and speed to two decimal places.
Frequently asked questions
- What pace gives a 25-minute 5K?
- For 5 km in 00:25:00, the constant pace is 05:00/km or 08:03/mi, with speed shown as 12.00 km/h.
- How is mile pace calculated?
- Multiply the unrounded seconds per km by 1.609344. At 05:00/km, mile pace displays as 08:03/mi. Switching split units keeps the distance and finish time unchanged.
- What happens to the final partial split?
- It gets its own row with its actual section time. For 5 km in 25:00, the mile rows reach 08:03, 16:06 and 24:08. The remaining 0.171968 km takes 00:52, and the final cumulative time is 25:00. Each cumulative time is rounded independently from the unrounded calculation.
- Does the calculated finish time predict my race result?
- No. It is the time for the selected distance at the entered constant pace, not a prediction based on a previous race.
Privacy on this page
Calculations run in your browser. Distance, time, pace and split settings are stored after # in the page URL and are passed along when you share that URL. Calculation inputs, results and copied text are not sent to the server or saved in browser storage.
To understand how the page is used and to improve the service, this page sends semku’s own usage statistics and automatic error reports. They go only to the dedicated endpoint under semku.com/api/telemetry/v1/. They are not used for advertising or third-party tracking.
The usage statistics include stages of use (such as starting an operation or requesting a copy), the times they occur and fixed identifiers that distinguish the page and feature. They do not include your distance, time, pace or split settings, the results shown or the text you copy. Inputs are not sent as hashes or as size categories either. The full URL and search terms are not sent.
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Calculations run in your browser; shared links include the input settings after #.