The formula
How to calculate half marathon pace
Pace is how long each mile takes on average across the whole run, found by dividing total time by total distance. It is the figure most training plans and race predictions are built around, rather than overall finish time.
A 2-hour half marathon works out to 9.16 minutes per mile — but that .16 is 16% of a minute, roughly 10 seconds, not 16 seconds, since the output is decimal minutes rather than minutes and seconds.
What to enter:
- Distance (miles) — the standard half marathon distance is 13.1 miles (21.1 km)
- Finish time (minutes) — convert hours to minutes first, e.g. 2 hours 5 minutes = 125
The result updates on every keystroke. The URL updates too, which makes the filled-in version easy to bookmark or send to someone else.
None of the fields above need specialist equipment to fill in — the inputs are the kind of measurements that can be taken at home with a tape measure or scale, which is exactly why this style of calculation is widely used as a first, approximate check rather than a diagnostic one.
Why half marathon pace matters
This kind of calculation gets used both out of general interest and ahead of a specific conversation — with a trainer, a midwife or a GP — where having an actual number ready, rather than a description, makes that conversation more concrete and specific.
It is most useful tracked over time rather than read once — a single reading tells you where you are today, while the same calculation repeated weeks or months apart, using the same method each time, shows the direction things are actually moving in.
A single number like this is most useful placed in context rather than read in isolation. Reference ranges exist because bodies vary considerably and still count as healthy across a wide spread of values, so a result sitting outside a commonly quoted range is a prompt to look more closely rather than a verdict on its own. The same figure, tracked consistently over time, tends to say more than any single reading ever will.
A calculator like this one is frequently used to prepare a specific number for an upcoming appointment, so that a description like "I think it has changed" can be replaced with an actual figure and a date it was measured on. Clinicians and trainers generally find a concrete number, however approximate, more useful to work from than a general impression.
Worked example
Work through the defaults on this page:
- Distance: 13.1 miles
- Finish time: 120 minutes
That gives:
- Average pace: 9.16 min/mile
Those starting figures exist only to show the calculation working, not as a target or a reference value to compare yourself against — replace them with your own measurements in the calculator above and the same formula applies exactly as shown.
Reading the result
Sub-8:00/mile is a strong club-runner pace for the distance; 10:00-11:00/mile covers a large share of finishers. Compare it to a recent 10K pace: half marathon pace typically runs 10-20 seconds per mile slower.
Where this goes wrong. The decimal output is easy to misread as minutes and seconds — 9.5 means 9 minutes 30 seconds, not 9 minutes 5 seconds. Multiply the decimal part by 60 to convert it to seconds.
As with any general-purpose formula, the result here is an estimate derived from population averages, not a measurement specific to you — a reasonable starting point for a conversation with a qualified professional, not a replacement for one. Nothing on this page is medical advice.
Around 11:00-13:00 per mile is a common realistic target for a first half marathon, finishing in roughly 2:25-2:50. Pace matters less than finishing comfortably on a first attempt.
Multiply minutes per mile by 0.621, or divide by 1.609. A 9:00/mile pace works out close to 5:36/km.
It returns average pace. With 13.1 miles distance and 120 minutes finish time, that comes to 9.16 min/mile. Change any field and the figure moves with it.
It uses a published formula applied exactly as defined, so the arithmetic itself is precise — but the formula is a population-level estimate, and individual results can vary from it for reasons the formula has no way to account for. Treat the output as a reasonable estimate rather than a measured or diagnostic value.
For most people, yes — a single reading is a snapshot, while the same measurement repeated consistently over weeks or months shows a trend, which is generally more informative than any one figure taken in isolation.
Small differences between calculators usually come down to which published formula or reference dataset each one uses — several equations in this area exist in more than one accepted version. This page states the specific formula used in the section above, so it is possible to check directly whether another source is using the same one.