Pace Calculator
Solve pace, finish time, or distance with exact mile and kilometer conversion, then build split times that add back to your displayed total.
Your result
Share these visible values
The copied link contains the values and settings shown in this calculator. It uses no account or server storage.
Split table
Split times are arithmetic at the entered constant pace. They are not a race prediction or training recommendation.
| Distance | Split | Cumulative |
|---|
Local and private: calculations and split tables stay in this browser. Analytics receives only bounded mode, unit, result-type and error-code labels—never your values or receipt.
Distance, time, and pace use one exact relationship
Average pace is elapsed time divided by distance. Finish time at a fixed pace is distance multiplied by pace, while distance is elapsed time divided by pace. The engine normalizes every value to metres and seconds with integer rational arithmetic before it formats a result.
One international mile is exactly 1,609.344 metres. The converter uses that NIST relationship rather than a shortened decimal, so changing between minutes per mile, minutes per kilometer, mph, and km/h does not accumulate hidden floating-point drift.
Common fixed-pace examples
These crawlable examples use constant pace and the same nearest-second rule as the calculator. They are calculation checks, not target recommendations.
| Distance | At 5:00/km | At 8:00/mile |
|---|---|---|
| 5K | 25:00 | 24:51 |
| 10K | 50:00 | 49:43 |
| Half marathon (21.0975 km) | 1:45:29 | 1:44:53 |
| Marathon (42.195 km) | 3:30:59 | 3:29:45 |
Why the split rows add up
Rounding each row on its own can make a table disagree with its finish time. This calculator first rounds each cumulative boundary, then subtracts adjacent boundaries. The last boundary is the displayed finish time, so the visible row durations reconcile exactly even when the final interval is partial.
For a negative split, you provide the exact seconds-per-unit change. The calculator applies half that change on either side of the target average pace over equal half-distances. A row that crosses halfway is calculated in two pieces. This describes arithmetic distribution only; it does not account for fitness, terrain, weather, fueling, injury risk, or whether a pace is suitable.
Limits and privacy
Distance is limited to 1,000 km, duration to 999:59:59, pace to 24:00:00 per selected unit, and split tables to 500 rows. Invalid values stay in the form with an inline explanation. The page does not use GPS, maps, training profiles, calorie estimates, accounts, cookies, local storage, or server calculations.
A copied receipt includes the normalized distance, rounded time, both pace units, both speed units, and the rounding note. A share link is created only when requested; it places the visible recipe in a versioned URL fragment rather than a query string.
Frequently asked questions
How do I calculate running pace?
Divide elapsed time by distance. This calculator keeps exact unit relationships internally, then rounds the displayed pace to the nearest whole second.
Can I calculate finish time from pace?
Yes. Choose Finish time, enter a distance and pace, and the calculator multiplies them. The result assumes the entered pace stays constant; it is arithmetic, not a prediction that you can sustain it.
What does 1:30 mean in a time field?
It means 1 minute 30 seconds. Enter an hour explicitly with three fields, such as 1:30:00 for 1 hour 30 minutes.
How are split times rounded?
The calculator rounds cumulative split boundaries to the nearest whole second, then subtracts adjacent boundaries. This keeps all displayed rows reconciled exactly to the displayed finish time.
What is a negative split here?
It is a user-defined arithmetic schedule where the second half is faster by a chosen number of seconds per kilometer or mile. It is not training advice or a race-performance forecast.
Does this calculator save or upload my run?
No. Calculation and split generation run locally without an account or application network request. Analytics receives bounded mode and unit labels, never your distance, time, pace, splits, receipt, query or URL fragment.
What is inside a shared link?
Only after you choose Share, its URL fragment contains the visible values and settings needed to reproduce the calculation. The page validates the state, removes the fragment after loading, and does not send it to analytics.
Sources and method
- BIPM — The International System of Units (SI Brochure), 9th edition
- NIST Handbook 133, Appendix E — General Tables of Units of Measurement
- NIST SP 811, Appendix B.8 — conversion factors
- NIST — Revised Unit Conversion Factors for the U.S. Survey Foot
- World Athletics — Technical Information and Competition Rules