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Pace calculator

Work out running pace, finish time or distance from the other two, in kilometres or miles. Enter any distance you like. With a split for every kilometre or mile and equivalent times at 5K, 10K, half and full marathon.

Training numbers, not medical advice

Estimate from a formula. Not a training plan or medical advice. Read the full note

These are arithmetic estimates from published formulas, not a training plan and not medical advice. They do not know your training history, injuries or health. Build up gradually, warm up, use a spotter for heavy lifts, and talk to a doctor before starting or intensifying training if you have any health condition. Stop and seek help for chest pain, dizziness or sharp joint pain.

What do you want to find?
Units
km

Common races: 5, 10, half marathon 21.0975, marathon 42.195.

h
min
s

Splits

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SplitCumulative time

Same effort at other distances

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DistancePredicted timePace

Pace, time and distance are three numbers tied together by one equation, so knowing any two gives you the third. Runners think in pace, race organisers publish times, and treadmills show speed, which is why the same run gets described three different ways. This calculator solves for whichever one you are missing and lays out the splits you need to hold.

How it is calculated

  1. Pace = time ÷ distance. A 10 km run in 50 minutes is 3000 s ÷ 10 km = 300 s per km, written 5:00 /km.
  2. Finish time = distance × pace. A marathon at 5:00 /km is 42.195 × 300 s = 3 h 30 min 59 s.
  3. Distance = time ÷ pace. An hour at 4:00 /km covers 15 km.
  4. Speed is the same information upside down: 60 ÷ pace in minutes per km gives km/h, so 5:00 /km is 12.0 km/h.
  5. A mile is 1.609344 km, so a pace per mile is the pace per km multiplied by 1.609344.

Example

You want to break 45 minutes for 10K. That is 2700 s ÷ 10 = 270 s per km, or 4:30 /km, which is 13.3 km/h and 7:14 per mile. The split table shows you should pass 5 km at 22:30 and 8 km at 36:00.

Predicting other distances

The equivalent times use Riegel's formula: T2 = T1 × (D2 ÷ D1)1.06. Peter Riegel fitted that exponent to world-record performances from 100 m to 100 miles in 1981, and it has held up well for distances between about 3 km and the marathon. It assumes you are equally trained for both distances, which is the catch: a 5K time converted to a marathon will flatter anyone who has not done the long runs. Riegel himself noted the exponent varies, closer to 1.08 for elite athletes.

Race distances

Racing well also depends on what you eat and drink around the effort: see the TDEE calculator for daily calories and the water intake calculator for fluid. A marathon is 42.195 km, fixed by the sport's governing body, and a half marathon is exactly half of that, 21.0975 km. The 5K and 10K are metric distances, 3.107 and 6.214 miles respectively, which is why mile splits in those races land on awkward numbers.

Frequently asked questions

How do I calculate running pace?

Divide your time by the distance. Thirty minutes for 5 km is 1800 s ÷ 5 = 360 s per km, or 6:00 /km. Choose "Pace" above, enter the distance and the time, and the calculator gives it per kilometre and per mile.

What pace do I need for a sub-4-hour marathon?

Just under 5:41 per kilometre, or 9:09 per mile. Set the distance to marathon, choose "Pace" and enter 3 h 59 min to see the split table for it.

How do I convert pace per kilometre to pace per mile?

Multiply by 1.609344. A pace of 5:00 /km is 8:03 /mi. The calculator shows both at once, whichever units you enter.

Can I predict my marathon time from a 10K?

Roughly, using Riegel’s formula, which is what the equivalents table does. Treat it as a ceiling rather than a prediction: it assumes marathon-specific training, so without the long runs the real time is usually slower.

What is a good running pace?

It depends entirely on distance, age and training. As orientation, many recreational runners sit between 5:30 and 7:00 per kilometre on an easy run, and easy pace should feel conversational whatever the number says.

Sources

  1. Riegel PS. Athletic records and human endurance. American Scientist, 1981 — source of the 1.06 endurance exponent
  2. World Athletics: Marathon discipline — for the official 42.195 km distance

By Calcelate Team. Formula from the sources above.

  1. 2026-09-15 · Formula and texts checked