How is running pace calculated?

Pace is total time divided by distance. A 25:00 (1500-second) 5 km run is 1500 ÷ 5 = 300 seconds per km, which is 5:00/km. To go the other way, multiply pace by distance: 300 s/km × 10 km = 3000 s = 50:00.

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

Multiply the per-km pace by 1.609344, the exact number of kilometres in a mile. A 5:00/km pace is 300 × 1.609344 ≈ 482.8 seconds, or 8:03 per mile. The per-mile pace is always the larger number because a mile is longer than a kilometre.

How do pace and speed relate?

Speed in km/h is 3600 divided by your pace in seconds per km. 5:00/km (300 s/km) is 3600 ÷ 300 = 12 km/h. Faster running means a smaller pace number but a larger speed number.

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

A marathon is 42.195 km. Four hours is 14,400 seconds, so 14,400 ÷ 42.195 ≈ 341 seconds per km, about 5:41/km (roughly 9:09 per mile). Use the "Finish time from pace + distance" tab to test any goal pace against the marathon distance.

Can I enter half marathon or marathon distances?

Yes — distance is a free decimal field in kilometres. Use 21.0975 for a half marathon and 42.195 for a marathon. You can enter any distance, including track repeats like 0.4 km.

Does this calculator store my data?

No. Every computation happens in your browser; nothing is sent to a server, and nothing is saved.

Running Pace Calculator

Time, distance, pace and speed — give any two, get the rest.

Pace is the runner's native unit: minutes and seconds to cover one kilometre or one mile. This calculator converts between the four quantities every runner tracks — finish time, distance, pace, and speed. Enter a recent run to learn your pace per km and per mile and your speed in km/h, or set a target pace to see what finish time it implies for any distance. Every calculation runs in your browser and uses the exact mile (1 mile = 1.609344 km), so the metric and imperial paces line up precisely.

Enter a finish time and distance to get your pace and speed

Time — minutes

Time — seconds

Distance (km)

Pace / km

5:00/km

Pace / mile

8:03/mi

Speed

12.00 km/h

25:00 ÷ 5 km = 5:00/km

How to use

Pick what you know
Two tabs at the top: "Pace from time + distance" (you ran a known distance in a known time) and "Finish time from pace + distance" (you have a goal pace and want a target finish time).
Enter your numbers
Time and pace are split into minutes and seconds so you never have to convert to total seconds by hand. Distance is in kilometres. The results update as you type — there is no submit button.
Read the results
The tinted boxes show pace per km, pace per mile, and speed (or finish time and speed). Invalid or empty inputs show a dash instead of a misleading number.

Worked examples

Run	Pace / km	Pace / mile	Speed
5 km in 25:00	5:00/km	8:03/mi	12.00 km/h
10 km in 50:00	5:00/km	8:03/mi	12.00 km/h
Half marathon (21.0975 km) in 1:45:00	4:58/km	8:01/mi	12.06 km/h
Marathon (42.195 km) in 4:00:00	5:41/km	9:09/mi	10.55 km/h

A clean reference point: 5:00/km is exactly 12 km/h, because 3600 s ÷ 300 s/km = 12. Equivalently it is 8:03 per mile.

Frequently asked questions

How is running pace calculated?: Pace is total time divided by distance. A 25:00 (1500-second) 5 km run is 1500 ÷ 5 = 300 seconds per km, which is 5:00/km. To go the other way, multiply pace by distance: 300 s/km × 10 km = 3000 s = 50:00.
How do I convert pace per km to pace per mile?: Multiply the per-km pace by 1.609344, the exact number of kilometres in a mile. A 5:00/km pace is 300 × 1.609344 ≈ 482.8 seconds, or 8:03 per mile. The per-mile pace is always the larger number because a mile is longer than a kilometre.
How do pace and speed relate?: Speed in km/h is 3600 divided by your pace in seconds per km. 5:00/km (300 s/km) is 3600 ÷ 300 = 12 km/h. Faster running means a smaller pace number but a larger speed number.
What pace do I need for a sub-4-hour marathon?: A marathon is 42.195 km. Four hours is 14,400 seconds, so 14,400 ÷ 42.195 ≈ 341 seconds per km, about 5:41/km (roughly 9:09 per mile). Use the "Finish time from pace + distance" tab to test any goal pace against the marathon distance.
Can I enter half marathon or marathon distances?: Yes — distance is a free decimal field in kilometres. Use 21.0975 for a half marathon and 42.195 for a marathon. You can enter any distance, including track repeats like 0.4 km.
Does this calculator store my data?: No. Every computation happens in your browser; nothing is sent to a server, and nothing is saved.

About

Why split time into minutes and seconds?

Runners read their watches in m:ss, not in total seconds. The widget accepts minutes and seconds separately and combines them internally, so a 1:45:00 half marathon is entered as it appears on your watch rather than as 6300 seconds.

Exact, not approximate, mile conversion

The metric-to-imperial pace conversion uses the internationally defined statute mile of exactly 1.609344 km (NIST Special Publication 811). That keeps the per-km and per-mile figures internally consistent — convert one to the other and back and you land on the same number.

Athletic, not medical

This is a training-and-racing tool for converting between pace, speed, time, and distance. It is not medical advice and makes no claims about fitness, health, or safe training loads.

Sources & references

Authoritative references behind the math, constants, and tables on this page. Verified by Buğra Sözeri on the dates shown and re-checked at every deploy.

NIST SP 811 — Guide for the Use of the International System of Units — Defines the exact statute mile (1 mile = 1.609344 km) used for per-km ↔ per-mile pace conversion(as of 2026-06-27)
World Athletics — Competition & Technical Rules — Standard road-race distances (5 km, 10 km, half marathon 21.0975 km, marathon 42.195 km) referenced in the worked examples(as of 2026-06-27)