Running Pace Calculator
Calculate pace, time or distance, get your splits, and predict times at every race distance.
Your run
Time taken
Race predictions below assume you have trained for the distance. No formula can tell whether you have put in the long runs a marathon needs, it only knows how fast you were over something shorter.
This converts between pace, time and distance: give it any two and it returns the third.
It also projects finish times at a given pace across the standard race distances.
How running pace works
Pace is time per unit distance, usually minutes per mile or per kilometre. It is the runner's inverse of speed, and it is more useful precisely because it answers the question you actually have: how long will this take?
Three quantities are locked together, so any two give the third. Running 5K in 25:00 is 8:03 per mile, or 5:00 per km.
The trap is assuming that pace holds across distances. At 8:03 per mile you would finish a marathon in 3:31, and almost nobody who runs a 25-minute 5K can do that. Race pace slows as distance grows, and the drop-off is substantial.
These are what the arithmetic gives. Real race times slow with distance, so a genuine marathon prediction from a 25-minute 5K is considerably slower than 3:31.
What to enter
- Distance
- In miles or kilometres, or a standard race distance. A marathon is 26.2188 miles, or 42.195 km.
- Time
- Total duration. Enter it with distance to get pace, or with pace to get distance.
- Pace
- Minutes per mile or per kilometre. Enter it with distance to project a finish time.
Standard race distances
- 5K
- 3.107 miles. The most common race distance.
- 10K
- 6.214 miles.
- Half marathon
- 13.109 miles, or 21.0975 km.
- Marathon
- 26.219 miles, or 42.195 km. The odd figure is a historical artefact of the 1908 London Olympics.
What this assumes
Projections assume an even pace held throughout. Real races involve terrain, weather, fatigue and pacing errors.
Race times do not scale linearly with distance. Projecting a marathon from a 5K time overestimates substantially without an endurance-aware model.
How to calculate your running pace
One relationship, read three ways.
- pace
- Minutes per mile or per km
- 1 mile
- 1.609344 km, which is the conversion between the two units
Convert the time to decimal minutes. 25:30 becomes 25.5. This is where most manual pace arithmetic goes wrong.
Divide by the distance. 25 minutes ÷ 3.107 miles = 8.05 minutes per mile.
Convert the decimal back. 0.05 × 60 = 3 seconds, so 8:03 per mile.
Project other distances carefully. Multiplying pace by distance gives an even-pace projection. For a realistic race prediction, expect to be slower over longer distances.
See a worked example: one 5K time, four distances
- Race
- 5K in 25:00
Pace: 25 ÷ 3.107 = 8:03 per mile, which is 5:00 per km.
At that pace: 10K in 50:00, a half marathon in 1:45, a marathon in 3:31.
Those are arithmetic, not predictions. A runner with a 25-minute 5K would more realistically expect a marathon well over four hours without specific endurance training.
The 5:00 per km figure is worth noting: it is one of the cleanest round paces there is, and a useful benchmark to train against.
8:03 per mile, or 5:00 per km
Frequently asked questions
- How do I convert between minutes per mile and per kilometre?
Divide the mile pace by 1.609 for kilometre pace, or multiply the kilometre pace by 1.609 for mile pace.
8:03 per mile is 5:00 per km. As a rough mental check, kilometre pace is about 62% of mile pace.
- Can I predict my marathon time from a 5K?
Not by multiplying. Even-pace arithmetic from a 25-minute 5K gives 3:31, and very few runners with that 5K time run a 3:31 marathon.
Prediction models such as Riegel's account for the slowdown with distance, and even those assume marathon-specific training. Endurance at 26 miles is a different quality from speed at 3.
- What is a good 5K time?
It depends entirely on age, sex and training history, so the honest answer is that it is relative. As rough orientation, under 30 minutes is a solid recreational time, under 25 is well-trained, and under 20 is competitive for most age groups.
The more useful comparison is against your own previous times, and against others in your age group rather than a general benchmark.
- Should I train at race pace?
Only for part of your training. Most endurance running should be easy, at a pace where you could hold a conversation, which is considerably slower than race pace.
The common error is running everything at a moderate effort: too hard to build an aerobic base, too easy to develop speed. Easy days easy and hard days hard is the durable pattern.
- Why is a marathon 26.2 miles?
The 1908 London Olympics. The course was extended so it could start at Windsor Castle and finish in front of the royal box, giving 26 miles 385 yards.
That figure was standardised in 1921 and has been the distance ever since. There is no physiological reason for it at all.
- How much does terrain affect pace?
A great deal. Hills, trails, wind and heat can all add a minute or more per mile compared with flat road running at the same effort.
This is why runners on hilly or trail courses often pace by effort or heart rate rather than by the watch. A pace target on a flat course becomes the wrong target on a hilly one.
Problems people actually run into
Setting a race goal by scaling up a shorter time
Multiplying a 5K pace out to a marathon gives a number that looks achievable and is not. 8:03 per mile for 3.1 miles is a very different demand from 26.2.
Use a prediction model that accounts for distance, and treat even that as conditional on having done the endurance training the distance requires.
Starting a race faster than goal pace
Fresh legs and adrenaline make the first mile feel easy at a pace that is unsustainable, and the time gained is repaid several times over later.
Even or slightly negative splits produce faster finishes for almost everyone. The discipline is in the first two miles, not the last two.
Results are estimates for general information only and are not professional financial, medical, or legal advice. Read our full disclaimer.
Last updated: September 4, 2026
