What this calculator works out
This calculator converts a distance and time into a running pace in minutes per kilometre and per mile, plus the equivalent speed.
Pace is the currency runners actually use. Race targets, training zones and split times are all quoted in minutes per kilometre or mile, and converting between them and speed is a constant small friction this removes.
Enter your details
Before you calculate
- Use chip time rather than gun time for race results, since it measures from when you crossed the start line.
- Enter distance in kilometres. A half marathon is 21.0975 km and a marathon is 42.195 km.
- Enter total time in minutes. A time of 1 hour 55 minutes is 115.
- Trail and hill running paces are not comparable with road paces; the terrain dominates.
Most training should be run at a conversational effort noticeably slower than race pace. A widely used approach puts around 80% of weekly volume at easy effort and 20% at hard effort, on the basis that running all sessions at a moderate middle pace produces neither the aerobic base nor the intensity adaptation.
How this calculator works
One division, expressed three ways:
Pace (min/km) = time in minutes ÷ distance in km
Pace (min/mile) = pace per km × 1.609
Speed (km/h) = distance ÷ (time ÷ 60)Pace is displayed in minutes and seconds. To convert a target finish time into a required pace, divide the target by the race distance — a sub-two-hour half marathon needs 120 ÷ 21.0975, or about 5:41 per kilometre.
Worked example: 10 km in 55 minutes
Using the default figures — 10 km in 55 minutes:
- Pace: 5:30 per km
- Pace: 8:51 per mile
- Speed: 10.9 km/h
To take that to a sub-50 minute 10 km, the required pace is 5:00 per kilometre — thirty seconds a kilometre faster, which is a substantial step rather than a minor adjustment. Seeing the target as a pace rather than a finish time makes the size of the gap much clearer, and it is the number you can actually check on the run.
Common mistakes
- Entering time in hours and minutes. Convert to total minutes first.
- Using 21 km for a half marathon. It is 21.0975, which changes the pace by a couple of seconds per kilometre.
- Comparing trail and road paces. Terrain differences swamp any fitness comparison.
- Training at race pace constantly. Most sessions should be considerably easier.
- Setting a target from a single good run. A pace held for 5 km rarely holds for 21.
Frequently asked questions
How do I predict a race time from a shorter distance?
Riegel's formula is the most commonly used: predicted time equals known time multiplied by the distance ratio raised to the power of 1.06. It tends to be optimistic for the marathon, where endurance and fuelling become limiting factors that a 10 km time cannot reveal.
What is a good 10 km time?
It depends entirely on age, experience and training. Rather than an absolute benchmark, a more useful comparison is your own previous times over the same distance and terrain. Parkrun publishes age-graded scores, which compare a performance against the world best for that age and sex and allow a fairer comparison over time.
Should I run to pace or to effort?
Effort, in most training. Pace does not account for heat, wind, hills, fatigue or how you slept, and holding a target pace on a bad day converts an easy run into a hard one. Racing is the exception, where a planned pace keeps you from starting too fast.
How much should I increase my training?
The commonly cited guideline is no more than about 10% additional weekly volume, though evidence for the specific figure is limited. The principle behind it is sound: most running injuries follow a sudden increase in load, and gradual progression with occasional easier weeks is more sustainable.
Is what I enter stored?
No. Distance and time are processed in your browser and never transmitted or retained.
Related tools
References
- NHS — running guidance, injury prevention and the Couch to 5K programme
- GOV.UK — UK Chief Medical Officers' physical activity guidelines
Sources are checked at publication and can change — how I choose and check references.