# Pace Calculator: Running Pace, Finish Time and Splits

Work out running pace per km, finish time or distance for 2.4 km, 5 km, 10 km, half and full marathons, with splits, 400 m lap times and race predictions.

Interactive tool: https://lookup.sg/tools/pace-calculator

## How this works
Pace is time divided by distance: a 10 km run in 60 minutes is 6:00 per km. Finish time is pace multiplied by distance, and distance is time divided by pace. Speed in km/h is 60 divided by the pace in minutes, and pace per mile is the per-km pace times 1.609.

Splits assume an even pace. A 2.4 km run, the distance in the IPPT, is six laps of a standard 400 m track, so it is split by lap; longer runs are split by kilometre, with the last split covering any part kilometre. The half marathon is 21.0975 km and the marathon 42.195 km.

Race predictions use Riegel's formula, T2 = T1 × (D2 ÷ D1)^1.06, which adds a little time for each doubling of distance. It works best between 5 km and the marathon for runners who have trained for the longer distance, and is less reliable from a short effort such as 2.4 km.

## FAQs
### What pace do I need to run 10 km in under an hour?
You need 6:00 per km, or 10 km/h, to run 10 km in exactly 60 minutes. That is 2:24 for every 400 m lap of a track.

### What pace is a 4-hour marathon?
A 4-hour marathon (42.195 km) needs an average pace of 5:41 per km. The same pace gives a half marathon in 2 hours.

### What pace is a 10-minute 2.4 km run?
A 10:00 2.4 km run is 4:10 per km, which is 1:40 for each of the six 400 m laps of a track, or 14.4 km/h.

### Can I predict my marathon time from a 10 km race?
Riegel's formula turns a 60-minute 10 km into about 2:12:23 for a half marathon and 4:36:01 for a marathon. Treat it as a guide: it assumes you have done the long-run training, and heat and humidity in Singapore usually add time.

## Sources
- [Riegel PS. Athletic records and human endurance. American Scientist 1981](https://www.jstor.org/stable/27850427)

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