Running apps, GPS watches, race results and treadmill displays all speak different languages — some show min/km, others min/mile, and treadmills almost always use mph or km/h. This converter bridges every format in one place, giving you all five speed representations simultaneously so you can plan training blocks, compare workouts across devices and predict finish times without reaching for a spreadsheet.
The core formulas
Running pace and speed are two views of the same quantity. The relationship is:
speed (km/h) = 60 ÷ pace (min/km)
For example a 5:00 min/km pace gives 60 ÷ 5 = 12 km/h. Going the other way:
pace (min/km) = 60 ÷ speed (km/h)
Converting between km/h and mph uses the fixed ratio 1 mile = 1.609344 km:
mph = km/h ÷ 1.609344 (or km/h = mph × 1.609344)
Between pace per km and pace per mile:
pace (sec/mi) = pace (sec/km) × 1.609344
Speed in metres per second (used in physiology and sprint coaching) is simply:
m/s = km/h ÷ 3.6
Race finish-time estimator
Finish time is the simplest calculation in running:
Finish time = pace (sec/km) × distance (km)
Select any preset distance — 5K, 10K, half marathon (21.0975 km), marathon (42.195 km), 50 km or 100 km ultra — or type a custom value. The result updates in real time as you adjust pace or speed. This is your even-split baseline: the time you would finish in if every kilometre were run at identical effort.
Worked example
A runner records 6.5 mph on a treadmill and wants to know their road running pace and projected marathon time.
- Convert to km/h: 6.5 × 1.609344 = 10.46 km/h
- Pace per km: 60 ÷ 10.46 = 5.74 min/km = 5:44 /km
- Pace per mile: 5.74 × 1.609344 = 9.24 min/mi = 9:14 /mi
- Marathon finish time: 5.74 × 60 sec × 42.195 km = 14,523 s = 4 h 02 m 03 s
Enter 6.5 mph in Speed → Pace mode and the calculator produces the same figures instantly.
Effort zones
The tool also categorises your speed into a rough training zone:
| Zone | Speed | Pace |
|---|---|---|
| Easy / Recovery | <8 km/h | >7:30 /km |
| Aerobic / Endurance | 8–11 km/h | 5:27–7:30 /km |
| Tempo / Threshold | 11–14 km/h | 4:17–5:27 /km |
| VO2max / Hard | 14–18 km/h | 3:20–4:17 /km |
| Sprint / All-out | >18 km/h | <3:20 /km |
These are approximate guides based on typical aerobic training zones. Your personal zones depend on fitness level, age and running economy.
Why two pace formats matter
Road races in Europe and most of the world are measured in kilometres; UK, US and Irish races traditionally use miles. GPS watches often default to one unit while race result services use the other. Knowing both simultaneously — as this calculator shows — means you never need to mentally convert on race day.
Every calculation runs entirely in your browser. No data is sent anywhere.