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Running Pace Calculator

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Pace, time and distance are one relationship with three unknowns, and this solves for whichever one you leave out. Set the two you know, pick kilometres or miles, and get the third — along with the split table you would actually carry into a race and an estimate of what the same fitness is worth over other distances.

What are you solving for
Measure in

How to use the running pace calculator

  1. 1Choose whether you want the pace, the finish time or the distance.
  2. 2Pick kilometres or miles. Everything on the page follows that choice, including the split table.
  3. 3Select a race distance or enter your own, and fill in the two values you already know.
  4. 4Enter pace as minutes and seconds, like 5:30. Time is split into hours, minutes and seconds.
  5. 5Press Calculate for the answer, the splits and the equivalent times at other distances.

Examples

Pace from a race result

Input
10K in 52:30
Result
5:15 per km — 8:27 per mile, 11.43 km/h

The same run expressed four ways. Pace per mile is always the larger number, because a mile is longer than a kilometre.

Target time from a target pace

Input
Marathon at 5:40 per km
Result
3:59:14

The classic sub-four marathon needs 5:41 per km, so 5:40 leaves less than a minute of margin over 42 km.

Splits for a half marathon

Input
21.0975 km at 5:00 per km
Result
1:45:29, with a final 0.0975 km split of 29 seconds

Race distances are not whole numbers. The remainder is shown as its own split rather than rounded away.

About the running pace calculator

Pace, speed and which one to think in

Pace and speed carry exactly the same information the opposite way round. Pace is time per unit distance and gets smaller as you get faster; speed is distance per unit time and gets larger. Runners almost universally think in pace and treadmills almost universally display speed, which is why the conversion appears on this page — 5:00 per kilometre is 12 km/h, and being able to move between them saves a lot of arithmetic at the gym.

The reason pace won among runners is that it is directly actionable. If you are aiming for a 45-minute 10K you need 4:30 per kilometre, and every kilometre marker gives you an immediate verdict on whether you are ahead or behind. A speed in kilometres per hour tells you the same thing but needs a division before it means anything at a marker post.

The one place pace misleads is in comparing efforts across distances. Being twenty seconds per kilometre slower over a marathon than over a 10K is not a decline in fitness, it is what the distance costs anyone. That gap is what the equivalent times above are trying to describe.

The awkward distances

Race distances are historical rather than tidy. A marathon is 42.195 km because of where the 1908 Olympic course started and finished, and a half is exactly half of that, 21.0975 km. In miles they come out at 26.2188 and 13.1094, which is why the last segment of a marathon measured in miles is a fifth of one and not a whole mile.

That fraction matters more than its size suggests. Runners pacing by mile markers often arrive at 26 miles believing the job is done, with a fifth of a mile still to run — around ninety seconds at a four-hour pace. Plans that ignore the remainder tend to be plans that miss the target by exactly that much. It is the reason the split table here shows the partial final segment explicitly rather than rounding the distance to something convenient.

The same applies at the short end. A 5K is 3.107 miles and a 10K is 6.214, so anyone converting a per-mile target into a finish time by multiplying by three or six will be optimistic by a noticeable margin. Working in metres throughout and converting once at the end, which is what happens here, avoids the compounding.

Frequently asked questions

Why is my watch pace different from the pace here?
Usually because your watch measured a longer distance than the course was. GPS wanders, and it wanders more under trees, between tall buildings and around bends, so a certified 10K frequently records as 10.1 or 10.2 km. Your average pace is then computed against that inflated distance and looks faster than the official result implies. The other cause is that watches show a rolling current pace, which swings with every stride, rather than the average over the whole run.
How reliable are the equivalent times?
They are a model, and the model is the one Peter Riegel published: the new time equals the known time multiplied by the ratio of the distances raised to the power 1.06. It was fitted to race results rather than derived from physiology, and it carries an assumption that quietly does most of the damage — that you are equally well trained for both distances. A fast 5K runner who has never gone beyond 10 km will not hit the marathon time it predicts, because that race is limited by endurance and fuelling rather than by speed.
What is a negative split and is it worth aiming for?
It means running the second half faster than the first, and yes — almost every distance record has been set that way. The reason is that going out too fast burns through carbohydrate early and raises lactate before the body has settled, and the time lost in the closing stages is far greater than the time gained at the start. The even splits shown here are a good plan precisely because they are hard to beat by starting fast; treat them as a ceiling for the first half.
Does the split table account for hills?
No, and no table can. These are even splits at a constant pace, which is what you want on a flat course and what you should deliberately ignore on a hilly one. On rolling terrain the useful approach is to hold effort constant rather than pace, letting the uphill splits run slow and the downhill ones run fast, and to compare the total against the target rather than each kilometre. Chasing a fixed pace up a climb is an efficient way to ruin the second half of a race.

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