Running Pace Calculator
Pace, finish time or distance — give it any two and it works out the third, in kilometres or miles, with every split.
Runs on your device — nothing you type is sent anywhereMinutes and seconds per kilometre.
Splits
The same effort elsewhere
Every number here assumes an even effort the whole way. A real race has hills, wind and a finish, and almost nobody runs a marathon at one pace.
How it works
Three steps, and the arithmetic runs in your browser.
Say which one you are missing
Pace, finish time, or distance. The two fields it needs appear; the one you asked for is the answer.
Fill in the other two
Kilometres or miles, your choice, and the race distances are one tap away.
Read the splits, not just the number
Every kilometre with the clock time you should see, and what the same effort is worth at the other race distances.
When this comes up
Working out what you just ran
A distance and a time off your watch, and the pace that produced them — in both units, because half the running internet uses the other one.
Chasing a finish time
Sub-four marathon, sub-two half, under fifty for the 10K. It gives you the pace that gets there and the clock time at every kilometre.
Writing a pace band
The splits table is the thing people scribble on their arm before a race. Here it is for any distance and any target.
Comparing two races
A 10K and a half are not comparable by time. Put both through the same formula and they are.
Pace, and what it can and cannot tell you
Pace is one division: the time you took over the distance you covered. What makes it useful rather than trivial is the direction you run it in. Divide time by distance and you learn what you did. Fix the pace instead and you learn what you have to hold, kilometre by kilometre, to arrive when you want to.
Any two of the three fix the third
Distance, time and pace are one equation with three names. Give it any two and there is exactly one answer for the missing one — no estimate, no model, nothing to disagree about. That is why this page asks which one you are missing first: the other two fields are all it needs, and showing you a third would only invite a contradiction.
One consequence worth knowing: a four-hour marathon and a two-hour half are the same pace, 5:41 per kilometre or 9:09 per mile. The half is exactly half the distance, so an even effort makes them the same number. Whether the second one is the same race is a different question, and the formula has no opinion on it.
Where the predictions stop being arithmetic
The last panel converts one performance into the others using Riegel's formula, which multiplies the time by the distance ratio raised to the power 1.06. Take a twenty-five minute 5K to the marathon and the multiplier is 9.59, so it predicts three hours fifty-nine.
That is real arithmetic on a curve fitted to race records, and it is genuinely useful between nearby distances. It is also making an assumption it cannot check: that you are as prepared for the long race as for the short one. A fast 5K is evidence about speed. A marathon asks for something a 5K never tests, and the formula has no way of knowing whether you have built it.
So read the far column as a ceiling on what your speed allows, not as a forecast of the day.
The splits assume something no race obeys
Every split on this page is an even one — the same pace from the gun to the line. Almost nobody runs that. Courses have hills, the first kilometre is always too fast, and the fastest way to run a long race is generally a little slower than average early and a little quicker late, which runners call a negative split.
The even splits are still the right thing to print, because they are the reference you are deviating from on purpose. Knowing you are twenty seconds up at 10K only means something against a number.
Kilometres and miles are the same run
A mile is 1.609344 kilometres exactly — that is a definition, not a measurement, agreed internationally in 1959. So 5:00 per kilometre is 8:03 per mile, and every pace here is shown both ways rather than making you convert it.
The race distances are metric even where the running is not: a marathon is 42.195 kilometres, which is 26.2188 miles, and a half is exactly half of that.
Nothing you type is sent anywhere
It is arithmetic in your browser. There is no account, nothing stored, and nothing transmitted — the same as everything else here.
Common questions
How do I calculate my running pace?
Divide the time by the distance. Put a distance and a time into this page and it does that division for you, showing the pace per kilometre and per mile, the speed in both units, and the clock time you should see at every split along the way.
What pace do I need for a four-hour marathon?
5:41 per kilometre, or 9:09 per mile, held the whole way. That is four hours divided by 42.195 kilometres. Because a half marathon is exactly half that distance, the same pace is also a two-hour half — the arithmetic makes those two targets identical.
How do I convert pace between kilometres and miles?
Multiply a per-kilometre pace by 1.609344 to get per mile, and divide to go back. So 5:00 per kilometre is 8:03 per mile, and 8:00 per mile is 4:58 per kilometre. This page shows both at once, so you do not have to.
Can it predict my marathon time from a 5K?
It will give you a number, using Riegel’s formula — a twenty-five minute 5K comes out as a 3:59 marathon. Treat that as what your speed permits rather than what the day will give you. The formula assumes you are as trained for the long distance as for the short one, and a 5K cannot show that.
What is a negative split?
Running the second half of a race slightly faster than the first. The splits on this page are even ones — the same pace throughout — which is the reference most race plans are written against rather than the way fast races are usually run.
Do I need an account?
No, and there is nothing to store. It is arithmetic running in your browser, with nothing transmitted at any point.
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