Pace Calculator
Pace is the language of running: minutes per kilometre or mile rather than speed. This calculator converts between distance, time and pace so you can plan a race target, check whether a training pace is realistic, and work out split times you can actually remember.
Inputs
Result
5:30 / km
Speed 10.91 km/h
How the pace calculator works
Pace = total time ÷ distance. Time = pace × distance. Speed in km/h = 60 ÷ pace in minutes per km.
Convert between units with 1 mile = 1.609 km: pace per mile = pace per km × 1.609.
Race prediction across distances uses Riegel's formula: T2 = T1 × (D2 ÷ D1)^1.06, where the exponent accounts for the fact that longer races are run slower.
Worked example: a 50-minute 10 km target
- Pace = 50 ÷ 10 = 5:00 per km, which is 8:03 per mile.
- Speed: 60 ÷ 5 = 12 km/h.
- 5 km split: 25:00. Every kilometre marker should read a clean multiple of five minutes.
- Riegel prediction for a half marathon: 50 × (21.0975 ÷ 10)^1.06 = 1h 44m.
- Marathon prediction from the same fitness: about 3h 37m, assuming appropriate endurance training.
Common mistakes to avoid
Racing every training run
Most weekly volume should be conversational. Training at race pace daily produces fatigue rather than adaptation.
Predicting a marathon from a 5 km time alone
Riegel assumes equivalent endurance training. Without the long-run base, real marathon times fall well short of the prediction.
Ignoring course and conditions
Heat, humidity, hills and wind can each add 10–30 seconds per kilometre. Pace to effort on hard days, not to the watch.
Frequently asked questions
How do I convert pace per km to per mile?
Multiply by 1.609. A 5:00 per km pace is 8:03 per mile.
What is a good 10 km time?
Around 50–60 minutes is solid for a recreational runner; sub-40 is competitive club level. Compare against your own progression first.
How do I predict a race time from a shorter race?
Use Riegel: new time = old time × (new distance ÷ old distance)^1.06, then add a margin if your long-run volume is limited.
Should I run negative splits?
Starting slightly slower than target and finishing faster generally produces better times than going out hard, especially over 10 km and beyond.
What pace should easy runs be?
Typically 60–90 seconds per kilometre slower than 10 km race pace — slow enough to hold a conversation throughout.
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