How it works
Running pace is time divided by distance — the inverse of speed. Total elapsed seconds = hours×3600 + minutes×60 + seconds. Pace per kilometre = total seconds ÷ distanceKm, expressed as minutes:seconds. Pace per mile = total seconds ÷ (distanceKm × 0.621371). Average speed km/h = distanceKm ÷ (total seconds ÷ 3600); mph = km/h × 0.621371. Worked example: 10 km in 0:50:00. Total time = 3,000 seconds. Pace/km = 3,000 ÷ 10 = 300 s = 5:00 per km. Distance in miles = 10 × 0.621371 = 6.214 mi. Pace/mile = 3,000 ÷ 6.214 ≈ 483 s = 8:03 per mile. Speed = 10 ÷ (3000/3600) = 12.0 km/h = 7.5 mph. Race planning uses pace to set even-effort splits — a marathon in 4:00 requires 5:41/km (9:09/mile) sustained. Negative splits (second half faster) feel harder on paper but often produce faster times because adrenaline and warmed muscles offset early caution. Hill and wind segments deviate from flat pace; GPS watches integrate terrain automatically but this calculator assumes steady effort.
Formula
Pace (s/km) = total seconds ÷ distanceKm | Speed (km/h) = distanceKm ÷ (total seconds / 3600)
Tips
- Add 10–15 seconds per km for hilly courses when planning from flat training pace.
- Half-marathon pace is typically ~5% slower than 10K race pace for trained runners.
- Convert treadmill km/h to pace if you train indoors — 12 km/h = 5:00/km exactly.
- Practice goal pace in the final long run segments before race day.
Frequently asked questions
- What pace is a 50-minute 10K?
- 5:00 per kilometre, 8:03 per mile, average speed 12.0 km/h (7.5 mph).
- How do I convert pace to treadmill speed?
- Speed (km/h) = 60 ÷ pace minutes. 5:00/km → 60÷5 = 12 km/h.
- What is a good 10K pace?
- Highly individual. Recreational runners often finish 45–60 minutes (4:30–6:00/km). Use your own recent race or time trial as baseline.
- Why are min/km and min/mile different numbers?
- A mile is 1.609 km — each mile takes longer in time at the same effort, so min/mile is a larger minute number than min/km.