Running Pace Calculator
h:mm:ss, or m:ss
Pace
5:00 /km
8:03 per mile
- 5K at this pace25:00
- 10K at this pace50:00
- One mile at this pace8:03
- Ten miles at this pace1:20:28
- Half marathon at this pace1:45:29
- Marathon at this pace3:30:59
How this was worked out
- Distance in metres10 km × 1,000 = 10,000 m
- Time in seconds50:00 = 3,000 s
- Pace = time ÷ distance3,000 s ÷ (10,000 ÷ 1,000) = 300 s = 5:00 /km
- Converted to the other unit300 s × 1,609 ÷ 1,000 = 8:03 /mi
The race times above are the same pace held the whole way, which is arithmetic rather than a forecast — nobody holds 5K pace for a marathon. To project a longer race from a shorter one, with the slowdown built in, use the marathon finish predictor, which applies Riegel’s and Cameron’s published formulas instead.
Distances here are the road distances World Athletics defines: the half marathon is 21.0975 km and the marathon 42.195 km, so a watch that measures 42.6 km on race day has drifted rather than found extra course. A mile is exactly 1609.344 m by the 1959 international agreement, which is where every conversion on this page starts. Clock times are rounded to the second only for display, so a column of them can differ from the total by a second or two.
Any two of the three fix the third
A run holds three numbers — how far, how long, how fast — and knowing two of them settles the third with no room left for judgement. That is the entire calculator: choose which one is missing, type the other two, read the answer. Solving for pace turns a finished run into the number you can compare with the next one. Solving for time answers what a distance will cost at a pace you already hold. Solving for distance answers how far a fixed slot of time will take you, which is the question most weekday runs actually pose.
Times can be typed the way you would say them. A colon form is read from the right, so 5:30 is five and a half minutes and 1:45:00 is an hour and three quarters. A number with no colon in it is minutes, because someone entering 6 means six minutes for a kilometre and someone entering 90 means an hour and a half — neither has ever meant six or ninety seconds.
One 10K, written five ways
Fifty minutes for ten kilometres is 5:00 per kilometre. The same run is 8:03 per mile, 12.00 km/h, 7.46 mph and 3.33 metres per second, and every one of those is the identical effort wearing a different label. Which label is useful depends on who you are talking to: a training partner in Berlin wants the first, a race in Boston wants the second, and a treadmill wants the third or fourth.
Hold that pace to the end of a marathon and the arithmetic says 3:30:59. Nobody should read that as a forecast — it is what the clock would show if the pace never moved, and pace always moves — but it does put a marathon goal and a 10K result on the same scale, which is where a season plan usually starts.
Effort is not evenly spread across the distances
The equivalent times shown under the result are one pace applied to every standard distance, and they get progressively less realistic as the distance grows. Ten kilometres at your 5K pace is already an unpleasant surprise; a marathon at it is not a race, it is a story about the last ten kilometres.
This matters because the two calculations look identical on screen and are not. Holding a pace over a longer distance is arithmetic. Predicting what you would actually run over a longer distance needs a model of how much you slow down, which is a different tool and a different set of published formulas.
What a pace number is worth
Pace is an output, not an instruction. It describes what happened over ground that had its own gradient, surface, wind and temperature, and none of that survives being averaged into one figure. Two 45-minute ten-kilometre runs, one on a still track and one into a headwind on trail, are the same number and nowhere near the same run.
It is still the most portable measure a runner has, because it needs no equipment beyond a clock and a known distance, and because everyone else uses it too. Treat it as a common currency for comparing your own runs with each other, and be sceptical the moment it is used to compare two runs that happened in different conditions.
5:00 per kilometre, in miles
Why does a 5:00 kilometre come out as 8:03 a mile and not 8:00?
Because a mile is a little over 1.609 kilometres, not 1.6 exactly, and the extra 0.009 is worth three seconds at that pace. Rounding the ratio is the single most common way a pace conversion goes quietly wrong.
Can I enter a distance that is not a standard race?
Yes. The preset list fills the field for the common road distances, but typing any number replaces it and switches the selection to a custom distance, so a 7.4 km loop or a 3.2 mile out-and-back works exactly the same way.
Which unit should I set the pace in?
Whichever one your races are marked in, since that is the number you will be checking on the move. The result panel gives you the other unit underneath regardless, so nothing is lost by picking the one you think in.
Is the marathon time in the list what I would run?
No. It is what the clock would read if you held the entered pace for 42.195 km without slowing, which is not what happens to anyone. For an estimate that models the slowdown, use a predictor built on the published endurance formulas instead.