Why use this calculator
Pace is the unit runners actually think in, and converting between distance, time and pace by hand is exactly the arithmetic nobody wants to do after a run. This calculator does it in both miles and kilometres, which matters because training plans, race distances and watch settings frequently mix the two.
The race projections are the more useful half: they show what your current fitness implies over longer distances, which is the reality check that keeps a first marathon goal honest. They also expose the most common racing mistake, which is starting at a pace that only works for the first few kilometres.
How to use it
- Enter the distance you covered and the time it took, splitting the time across hours, minutes and seconds.
- The distance field is in miles, so convert from kilometres first if that is how your watch records. 5 kilometres is 3.1 miles.
- Use a run you completed at a genuine effort rather than an easy session, because the projections assume the pace reflects your current capability.
- The projected times for longer distances apply a standard endurance relationship, so treat them as a ceiling on race day rather than a plan, particularly if your longest run is far shorter than the distance being projected.
What each result means
- 400 m lap
- Time for one lap of a standard 400 metre track at this pace, the number to watch on a track session or a lap counter.
- Pace (per mile)
- Minutes and seconds to cover one mile at this effort. The standard unit in the United States and the United Kingdom.
- Pace (per km)
- The same effort expressed per kilometre, which is how most of the world and most race splits are measured.
- Speed
- Your average speed in miles per hour, useful for comparing against a treadmill setting.
- 5K Time
- Projected 5 kilometre finish time at this pace. The most reliable of the projections for most runners.
- 10K Time
- Projected 10 kilometre finish. Realistic if you have run close to that distance in training.
- Half Marathon
- Projected 21.1 kilometre finish. Optimistic unless your long runs are well into double figures.
- Marathon
- Projected 42.2 kilometre finish assuming pace holds. It rarely does without substantial endurance training behind it.
The formula
Pace is total time divided by distance, expressed as minutes and seconds per unit. Speed is distance divided by time. Converting between imperial and metric pace uses the factor 1.60934 kilometres per mile, so a per-mile pace divided by 1.60934 gives the per-kilometre equivalent. Race projections multiply your pace by the target distance in the same units, 3.10686 for 5K, 6.21371 for 10K, 13.1094 for a half marathon and 26.2188 for a marathon, which assumes pace holds across distance.
How this number is used in practice
Race projections assume pace transfers across distance, and it does not do so evenly. Most runners slow by several per cent for each doubling of distance, and the drop-off is far larger for anyone whose longest training run falls well short of the race. A 5K time is a reasonable predictor of a 10K; the same 5K time predicting a marathon is a fitness ceiling rather than a plan, and treating it as a target is how people blow up at 30 kilometres.
The most common race-day error is starting faster than goal pace because it feels easy in the first kilometre. Almost every well-executed race is run as a negative split, with the second half slightly faster than the first, and almost every disaster starts the other way round.
Course profile, heat, humidity and wind all shift realistic pace by more than most runners allow for, which is why pacing to effort often beats pacing to a watch.
Worked examples
5K (3.1 miles) in 25 minutes
8:04 per mile or 5:01 per kilometre, projecting a 50:07 10K and a 1:45:43 half marathon.
10 miles in 80 minutes
8:00 per mile at 7.5 mph, projecting a 24:51 5K.
26.2 miles in 4 hours
9:09 per mile or 5:41 per kilometre, an even marathon pace throughout.
When people use it
- Working out your pace from a training run
- Setting a realistic race-day target from current fitness
- Converting between mile and kilometre pace for a training plan
- Checking whether a goal time is plausible before committing to it
- Planning splits for an even or negative-split race
Tips
- Start races slower than goal pace and aim for a negative split. Nearly every good race is run that way.
- Expect to slow by several per cent for each doubling of distance, more if your long runs are short.
- Heat, humidity, wind and hills shift realistic pace substantially; run to effort rather than to the watch.
- Most training should be genuinely easy, conversational pace, with only a small share at hard effort.
- Projections assume endurance to match. A marathon estimate from a 5K means little without long runs behind it.
- Treadmill pace runs slightly easier than road pace; a 1 per cent incline is the usual correction.
What it assumes, and where it stops being accurate
- Pace is assumed constant across the distance, which no real race achieves exactly.
- Race projections apply a standard endurance relationship and ignore your actual training volume.
- Terrain, elevation, surface, weather and altitude are not modelled.
- Distance is entered in miles; kilometre figures must be converted before entry.
- The projections assume adequate endurance for the target distance, which is often the real limiting factor.
Terms used on this page
- Pace
- Time taken to cover one unit of distance, usually minutes per mile or per kilometre.
- Negative split
- Running the second half of a race slightly faster than the first.
- Threshold pace
- The effort you could sustain for roughly an hour, used to build sustainable speed.
- Taper
- A planned reduction in training volume before a race so you arrive fresh.
Questions people ask
- What is a good running pace?
- It depends entirely on training age and goals. A beginner might run 10 to 12 minutes per mile comfortably, an intermediate runner 8 to 10, and an experienced one under 7. The more useful comparison is against your own previous times, since pace varies enormously with terrain, weather and where you are in a training block.
- How do I convert pace between miles and kilometres?
- Divide a per-mile pace by 1.60934 to get per kilometre, or multiply the other way. An 8:00 mile is about 4:58 per kilometre. For mental arithmetic, a per-kilometre pace is roughly 60 per cent of the per-mile figure, which is close enough to sanity-check a watch setting.
- Are the race time projections reliable?
- For distances close to the one you entered, yes. A 5K time predicts a 10K reasonably well. Longer projections assume endurance you may not have. Most runners slow by several per cent per doubling of distance, and far more if their long runs fall well short of the race distance.
- Should I run all my training at goal pace?
- No. Most established training approaches put the large majority of weekly volume at genuinely easy, conversational effort, with a small share at threshold or interval pace. Running everything at a moderate-hard effort accumulates fatigue without producing the adaptations of either easy or hard work.
- Why is my race pace slower than my training pace?
- Usually it should not be. Race pace is normally faster over the same distance. If a race comes in slower, the common causes are starting too fast and fading, heat or humidity, a hillier course, or an inadequate taper. Comparing a flat solo time trial against a crowded hilly race is not comparing like with like.
Use this with
Running Pace Calculator answers one part of the question. These pick up where it stops: Calories Burned Calculator, Heart Rate Zones Calculator, BMR Calculator and Water Intake Calculator.
Where these figures come from
This calculation is jurisdiction-neutral arithmetic. No country-specific rules are applied.
- American College of Sports Medicine: resources. Exercise testing and prescription guidance
- Heart Foundation: physical activity and exercise. Activity guidance for adults
Running Pace Calculator produces an estimate for general information. It is not financial, tax, medical, legal or engineering advice. read the full disclaimer. Spotted a wrong number? Report it and it gets fixed. The form picks up this calculator and the inputs you used.