Running Pace Calculator
Enter the distance and time of any run to see your pace per kilometre and per mile, speed in km/h and mph, and projected finish times at the standard race distances — 5K, 10K, half marathon and marathon.
Average pace per km
05:00 / km
- Pace per km
- 05:00 / km
- Pace per mile
- 08:03 / mi
- Speed
- 12.00 km/h
- Speed (mph)
- 7.46 mph
- Finish time — 5K (5 km)
- 25:00
- Finish time — 10K (10 km)
- 50:00
- Finish time — Half marathon (21.0975 km)
- 1:45:29
- Finish time — Marathon (42.195 km)
- 3:30:59
Pace = total time ÷ distance. Finish times for 5K, 10K, half marathon (21.0975 km) and marathon (42.195 km — World Athletics standard) project the average pace at constant effort. Mile ↔ kilometre uses the NIST exact factor 1 mile = 1.609344 km.
How to use this calculator
Enter how far you ran in the Distance field and pick the unit (kilometres or miles). Then enter the total time in hours, minutes and seconds. The headline number is your average pace in the chosen unit. The breakdown shows pace per kilometre and per mile, speed in km/h and mph, and the projected finish time at the four standard road-race distances — 5K, 10K, half marathon (21.0975 km) and marathon (42.195 km). The projections assume an even effort across the full distance; in practice longer races slow because of glycogen depletion and thermoregulation, so treat marathon projections from short runs as an optimistic ceiling rather than a prediction.
How the calculation works
Pace and speed are the same physical relationship written two ways: pace equals total time divided by distance covered, and speed equals distance divided by total time. The calculator computes total seconds from your hours, minutes and seconds inputs, then divides by the distance to get pace per unit; the reciprocal gives speed. Mile-to-kilometre conversion uses the NIST exact factor 1 international mile = 1.609344 kilometres (NIST SP 811:2008, Appendix B.8), so converting km/h to mph multiplies by 0.6213711922… exactly. The standard race distances are set by World Athletics (formerly the IAAF) in Technical Rule TR4.3 "Distances of Road Races": 5 km, 10 km, 21.0975 km for the half marathon and 42.195 km for the marathon, with the marathon distance fixed at the 1908 London Olympics and codified internationally in 1921.
Worked example
A 5 km training run in 25 minutes flat is an average pace of 25 ÷ 5 = 5:00 per km. The reciprocal speed is 5 km ÷ (25/60) h = 12.00 km/h, or 12 × 0.6213712 ≈ 7.46 mph. Per mile: 25 min × 1.609344 / 5 = 8:02 per mile. Project that pace to the marathon: 42.195 km × 5:00 per km = 210.975 minutes = 3 hours 30 minutes 59 seconds. The same pace finishes a half marathon in 21.0975 × 5 = 105 minutes 29 seconds, and a 10K in 50 minutes flat.
Frequently asked questions
How is running pace calculated?
Pace equals total time divided by distance. For a 5 km run in 25:00, that is 25 minutes ÷ 5 km = 5:00 per km. To convert to pace per mile, multiply by 1.609344 (the exact NIST conversion factor for one international mile to kilometres). To convert pace to speed in km/h, divide 3600 by the pace in seconds per km — for example, 300 seconds per km gives 3600 ÷ 300 = 12 km/h.
What is the difference between pace and speed?
They are the same physical quantity written two ways. Speed is distance covered per unit of time (km/h, mph) and pace is time taken per unit of distance (min:sec per km, per mile). Runners typically think in pace because it is easier to target — "5:00 per km" is concrete in a way that "12 km/h" is not when you can see your watch tick over each kilometre marker. Cyclists and motorists prefer speed because they move fast enough that distance per hour is more legible.
Are the projected finish times accurate for marathons?
They project the mathematical pace at constant effort, which is an upper bound on what is realistic for longer distances. Real marathon finish times are almost always slower than a marathon-equivalent projection from a 5K or 10K, because aerobic capacity, glycogen stores and thermoregulation all degrade across hours of running. The classic Riegel model T₂ = T₁ × (D₂/D₁)^1.06 corrects for this fatigue exponent; that gives a more realistic prediction than the pure-pace projection here. Use this calculator for the maths; use a Riegel or VDOT chart for race-day predictions.
What are the exact standard race distances?
The road racing distances set by World Athletics (formerly the IAAF) in Technical Rule TR4.3 are: 5 km, 10 km, 15 km, 20 km, half marathon at 21.0975 km, 25 km, 30 km, and marathon at 42.195 km. The marathon was fixed at the 1908 London Olympics — 26 miles from Windsor Castle to the White City stadium plus 385 yards to finish in front of the royal box, totalling 42.195 km — and codified for international competition by the IAAF in 1921. Five kilometres equals 3.107 miles, the marathon equals 26.219 miles, and the half marathon equals 13.109 miles.
How do I convert between minutes per kilometre and minutes per mile?
One mile is 1.609344 kilometres exactly (NIST). So pace per mile equals pace per km multiplied by 1.609344. A 5:00 per km pace is 5 × 1.609344 = 8.047 minutes per mile, or about 8:02.8 per mile. Going the other direction: 8:00 per mile is 8 ÷ 1.609344 = 4.971 minutes per km, or about 4:58.3 per km. As a rule of thumb, pace per mile is about 60 % slower than pace per km because a mile is about 60 % longer.
What is a good 5K time?
It depends on age, sex and training. World Athletics outdoor world records are 12:35 (Joshua Cheptegei, 2020) and 14:00 (Beatrice Chebet, 2024). For amateur runners, parkrun median 5K times are around 28-32 minutes; sub-25 is solid for a recreational runner, sub-20 is club-quality, and sub-18 is competitive at most local races. Use this calculator to back-project from your goal pace — for sub-25, target 5:00 per km; for sub-20, target 4:00 per km.
Why is the marathon 42.195 km and not a round number?
The 1908 London Olympics marathon ran from Windsor Castle to the White City stadium — about 26 miles — with an extra 385 yards added so the finish would be in front of King Edward VII's royal box. That distance, 26 miles 385 yards = 42.195 km, was adopted by the IAAF in 1921 as the official marathon distance and has not changed since. The half marathon at 21.0975 km is exactly half of this.