Running Pace Calculator
A distance and a time give a pace, and a pace gives every other distance. The race times here are that pace held exactly, which nobody does — real pace fades with distance.
Pace
5:00per km
- Per kilometre
- 5:00
- Per mile
- 8:03
- Speed
- 12.00 km/h
- Speed
- 7.46 mph
- 5K
- 25:00
- 10K
- 50:00
- Half marathon
- 1:45:29
- Marathon
- 3:30:59
- The race times are that pace held exactly, which nobody does over every distance. A marathon at 5K pace is not a prediction, it is arithmetic — real pace fades with distance, typically by several per cent per doubling.
- Splits are usually written as minutes and seconds per kilometre or mile, which is what the first two figures are. Treadmills use speed instead, which is the same thing upside down.
About the pace calculator
Pace is time divided by distance, written as minutes and seconds per kilometre or per mile. Fifty minutes for ten kilometres is a 5:00 pace, which is 8:03 per mile and 12 km/h — the same effort expressed three ways, because treadmills use speed while runners use pace.
The race predictions are arithmetic rather than forecasts. Holding 5:00 per kilometre for a marathon gives 3:30:59, and almost nobody who runs a 50-minute 10K will do that. Real pace fades with distance — typically by several per cent per doubling — which is why proper race predictors apply an exponent rather than multiplying.
What the projections are genuinely useful for is the other direction: if you want a particular finish time, they tell you the pace you have to hold, and you can find out on a training run whether that pace is realistic. A goal marathon pace should feel comfortable for an hour.
For interval work the same arithmetic gives split times. A 400-metre repeat at 5:00 per kilometre pace is 2:00, and knowing that before you start is more useful than working it out mid-session.
What it works out
- Pace per kilometre and per mile
- Speed in km/h and mph
- Times over 5K, 10K, half marathon and marathon
The formula
Pace = Time ÷ Distance Speed = Distance ÷ Time
Fifty minutes is 3,000 seconds. Divided by ten kilometres, that is 300 seconds per kilometre — written as 5:00.
Per mile, multiply by 1.609344: 483 seconds, or 8:03. Speed is the same relationship inverted, so 3,600 seconds divided by a 300-second kilometre is 12 km/h, which is 7.46 mph.
Race times come from holding that pace across the distance. Five kilometres is 25:00, ten is 50:00, a half marathon at 21.0975km is 1:45:29 and a marathon at 42.195km is 3:30:59.
Those last two are where arithmetic and reality part company. Endurance falls off with distance for everyone, so a real marathon from a 50-minute 10K runner is considerably slower than 3:30. Proper race predictors raise the distance ratio to a power of about 1.06 to capture that fade; this does not, and says so rather than implying a prediction.
- Time
- Hours, minutes and seconds for the distance covered.
- Distance
- In kilometres or miles.
- Pace
- Minutes and seconds per unit of distance. How runners talk.
- Speed
- Distance per hour. How treadmills talk.
A worked example
Ten kilometres in fifty minutes.
That works out to 5:00 per km.
- Per kilometre
- 5:00
- Per mile
- 8:03
- Speed
- 12.00 km/h
- Speed
- 7.46 mph
- 5K
- 25:00
- 10K
- 50:00
- Half marathon
- 1:45:29
- Marathon
- 3:30:59
Questions
What pace is a 50 minute 10K?
5:00 per kilometre, or 8:03 per mile, which is 12 km/h. The same effort described three different ways.
How do I convert pace per km to per mile?
Multiply by 1.609. A 5:00 kilometre is an 8:03 mile. Going the other way, divide — an 8:00 mile is a 4:58 kilometre.
Are the race times predictions?
No, they are that pace held exactly across the distance. Real pace fades with distance, so a marathon run at your 10K pace is not going to happen. Use them to find a target pace, not to predict a result.
How much slower should marathon pace be than 10K pace?
Commonly around 10 to 15 per cent slower for a trained runner, and more for someone with less endurance base. Proper predictors use an exponent on the distance ratio rather than a flat percentage.
What is a good 5K time?
It depends entirely on age, sex and training. Under 30 minutes is a common first milestone, under 25 is solid for a recreational runner, and under 20 is genuinely quick. The only useful comparison is against your own previous times.
How do I work out interval splits?
The same division. At 5:00 per kilometre, a 400-metre repeat is 2:00 and an 800 is 4:00. Enter the interval distance and your target pace time to get it directly.
Should I train at race pace?
Not for most of your volume. The bulk of training is better done well below race pace, in zone 2, with a smaller amount at or above it. Running everything at goal pace is a reliable way to arrive at a race tired.