Running Pace Calculator — Time, Distance & Splits
Calculate running pace, finish time, or distance with only the two values you know, then optionally build exact even or negative splits.
Plan your pace, then explore each checkpoint
Enter the two values you know. Switching miles, kilometers or calculation mode keeps the same run. Examples are planning scenarios, not training recommendations.
Average pace
5:15/km10 km in 52:30
Plan even or negative splits
A negative split allocates more time to the first half and less to the second while keeping the same finish time.
Your checkpoint plan
Even pace throughout: 5:15/km.
This interval: 1 km in 5:15.
Full split table
| Checkpoint | Interval | Time | Arrival |
|---|
Interval times are differences between rounded arrivals, so the displayed times add up to the displayed finish. Sub-minute runs use milliseconds; other plans use whole seconds.
Other distances at this same average pace
These hold pace constant. They do not predict your ability to sustain it or account for terrain, fatigue, weather or stops.
Try a complete plan
Calculation, rounding and units
Pace = time ÷ distance. Time = pace × distance. Distance = time ÷ pace. One international mile is exactly 1.609344 km. The marathon example uses 42.195 km and the half marathon 21.0975 km.
For a negative split ratio r, first-half pace = 2 × average pace ÷ (2 − r); second-half pace = first-half pace × (1 − r). A checkpoint interval crossing halfway combines both paces. Halfway is the exact midpoint, not the nearest whole kilometer or mile.
Exact fractions preserve the run when you change units or modes. Editable computed values display up to 12 distance decimals or millisecond time precision; the exact value stays in memory until you edit that field. Pace displays may have milliseconds. Split intervals are derived from rounded arrival times, so a one-second difference between equal-distance intervals can be display rounding rather than a change in the plan.
Limits and privacy
Software limits: distance 0.001–1,000 km; average pace 1 second–60 minutes per km; positive finish time up to 1,000 hours; negative split 0–20%. Checkpoints every 1 or 5 selected distance units, up to 1,000 rows. These limits do not establish a safe or achievable running pace.
Use a decimal dot, without grouping commas or exponents. Distance accepts up to 12 decimals, time seconds up to 3, and the negative-split percentage up to 3. Invalid values stay editable and hide the old result. Running values are not automatically saved or added to your URL. Copy, CSV and print are explicit actions on this device.
Sources: NIST international mile conversion; World Athletics marathon distance. This calculator plans arithmetic splits; it does not prescribe exercise or forecast performance.
