Running Pace Calculator
Enter a distance and finish time to get pace per km / per mile and average speed, or switch to "Finish time from pace" to project a finish time and per-km splits from a target pace. Covers training intervals and race plans for 5K, 10K, half- and full-marathon distances.
Please enter a valid number
Pace per km
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Pace per mile
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Average speed (km/h)
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Average speed (mph)
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Split times (cumulative per km)
| km | cum. |
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Idealised constant-pace splits — real races vary with terrain, weather, fuelling and pace drift.
Pure arithmetic — actual race times depend on terrain, weather, fuelling and heart rate.
Formula
Pace (s/km) = total time (s) ÷ distance (km) Pace (s/mi) = pace (s/km) × 1.609344 Average speed (km/h) = distance (km) ÷ time (h) Finish time = distance × pace
- · 1 mile = 1.609344 km (international agreement) — every km↔mile conversion uses this constant.
- · Official race distances: 5K = 5.000 km, 10K = 10.000 km, half marathon = 21.0975 km, marathon = 42.195 km (World Athletics).
- · Time input accepts mm:ss (e.g. 50:00) and h:mm:ss (e.g. 1:45:30); minutes and seconds must be below 60.
- · Pace input is mm:ss per km (e.g. 5:30 means 5 minutes 30 seconds per kilometre).
- · Per-km splits assume you hold the target pace for the entire distance; real races almost always show pace drift of 1–5% slower in the second half due to fatigue, terrain and fuelling.
- · For projecting times across different race distances, see the Riegel formula: T₂ = T₁ × (D₂ ÷ D₁)^1.06. This tool only handles constant-pace scenarios.
- · References: World Athletics competition rules; Jack Daniels, "Daniels' Running Formula" — for pacing theory.
Frequently asked
What is 5:00 /km in km/h and mph?
A pace of 5:00 per km is 300 s/km, which equals 12 km/h (60 ÷ 5 = 12). In imperial that's 5:00 × 1.609344 ≈ 8:02 per mile, or about 7.46 mph. This is a typical jogging-to-entry-level-marathon pace (a steady 5:00/km gets you a 4:13:00 marathon finish).
What is the difference between pace and speed?
They are reciprocals of the same information. Speed (km/h) = distance ÷ time. Pace (min/km) = time ÷ distance. Runners prefer pace because it is easier to do mental math on ("how many minutes is this kilometre?"), while cyclists and drivers use speed. Conversion: km/h = 60 ÷ pace-minutes-per-km.
Why do my actual races run slower than the calculator predicts?
The calculator assumes a perfectly even pace from start to finish. In real races your muscle glycogen depletes, heart rate drifts upward at the same workload (cardiac drift), and aid stations cost a few seconds each. The result is a "positive split" of roughly 1–5% over a half- or full-marathon. The Riegel race-prediction formula T₂ = T₁ × (D₂ ÷ D₁)^1.06 uses the 1.06 exponent to model exactly this fatigue penalty.
Can I convert a treadmill display back into a pace?
Yes. The simplest mental shortcut is pace (min/km) = 60 ÷ speed (km/h); pace (min/mi) = 60 ÷ speed (mph). For example, a treadmill set to 10 km/h gives a pace of 6:00 per km. You can also enter 1 km in the "Pace from time" mode and adjust the time until the pace matches your treadmill speed.
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