Running Pace Calculator
Pace, speed and finish-time predictions.
Pace (min/km) and speed (km/h) are two views of the same effort — runners think in pace, treadmills in speed.
How to use
- Predict: enter race distance and your training pace.
- Or reverse: enter distance and a finish time for the pace.
- Speed in km/h is shown too.
About this tool
Predictions assume even pacing; real races vary with hills, weather and race-day adrenaline.
All math runs in your browser.
How it works
Pace and speed are two views of the same thing. Pace = time ÷ distance (e.g. 25 minutes ÷ 5 km = 5:00 per km); speed = distance ÷ time (12 km/h). They are reciprocals: pace in min/km = 60 ÷ speed in km/h. Runners talk pace, cyclists talk speed — the math is identical.
Predicting a finish time from a known performance uses the Riegel formula: T2 = T1 × (D2/D1)^1.06. The 1.06 exponent captures the fact that pace fades slightly as distance grows; for trained runners it predicts times between about 4 minutes and 4 hours remarkably well.
Watch the units: 1 mile = 1.60934 km, so a 8:00/mile pace equals about 4:58/km. Mixing the two is the classic race-day error — always confirm which unit your plan uses.
Worked examples
From 5K to 10K: You run 5K in 25:00 — that is 5:00/km, or 12 km/h. Riegel predicts your 10K: 25:00 × 2^1.06 ≈ 25:00 × 2.083 ≈ 52:05.
Marathon goal pace: Aiming for a 4-hour marathon (42.195 km)? You need 5:41 per km, every kilometre. Your half-marathon equivalent at the same fitness: about 1:55.
Quick reference
| Pace (min/km) | Speed (km/h) | 5K time | 10K time |
|---|---|---|---|
| 4:00 | 15.0 | 20:00 | 40:00 |
| 5:00 | 12.0 | 25:00 | 50:00 |
| 6:00 | 10.0 | 30:00 | 1:00:00 |
| 7:00 | 8.6 | 35:00 | 1:10:00 |
| 8:00 | 7.5 | 40:00 | 1:20:00 |
Frequently asked questions
What is a good 10k pace?
Recreational runners often run 6:00–7:30/km; sub-50-minute 10k needs ~5:00/km.
How do I convert min/km to km/h?
Divide 60 by the pace in minutes: 5:00/km = 12 km/h.
Is my data stored?
No.
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