How the calculator works it out
Pace, time and distance are tied together by one simple relationship, so any two give you the third. Pace is time per unit of distance; speed is the same thing turned upside down.
Pace = time ÷ distance
Time = pace × distance
Distance = time ÷ pace
Speed (mph) = 60 ÷ pace in minutes per mile
1 mile = 1.609344 km
The calculator keeps everything in seconds and kilometres while it works and converts at the end, so switching between miles and kilometres never adds rounding errors. Times are shown to the nearest second.
Worked example: a 4-hour marathon
A marathon is 42.195 km, which is 42.195 ÷ 1.609344 = 26.22 miles. Four hours is 14,400 seconds. The pace is 14,400 ÷ 26.22 = 549.2 seconds a mile, which is 9:09 per mile, or 14,400 ÷ 42.195 = 341.3 seconds, 5:41 per km. That is a speed of 6.6 mph or 10.5 km/h. At an even pace you pass the halfway mark at about 2:00:00 and mile 20 at about 3:03:04. This marathon loads when the page opens.
Race distances
| Race | Kilometres | Miles |
|---|---|---|
| 5K | 5 | 3.11 |
| 10K | 10 | 6.21 |
| Half marathon | 21.0975 | 13.11 |
| Marathon | 42.195 | 26.22 |
The marathon distance of 42.195 km and the half at exactly half of it are the standard road distances used by World Athletics competition rules. The mile conversion uses the international mile, defined as exactly 1,609.344 metres by the National Institute of Standards and Technology.
Limits
- Splits assume an even pace the whole way. Real races have hills, turns, wind and aid stations.
- GPS watches often measure a race a little long because runners rarely take the shortest line, so your watch pace may look faster than your official pace.
- For walking calories at a given pace, see the calories burned walking calculator.
Questions people ask
How do I work out my running pace?
Divide your time by your distance. A 4-hour marathon is 240 minutes over 26.22 miles, which is 9.15 minutes a mile, or 9:09 per mile. Per kilometre it is 240 ÷ 42.195 = 5.69 minutes, or 5:41 per km. Enter the time and distance above and the calculator does the division and the conversion.
What pace do I need for a sub-2-hour half marathon?
A half marathon is 21.0975 km, or 13.11 miles. Two hours is 7,200 seconds, so the pace is 7,200 ÷ 13.11 = 549 seconds a mile, which is 9:09 per mile or 5:41 per km. Run a few seconds a mile faster than that to leave room for water stops and crowded starts.
How long is a 5K, 10K, half marathon and marathon?
A 5K is 5 km (3.11 miles), a 10K is 10 km (6.21 miles), a half marathon is 21.0975 km (13.11 miles) and a marathon is 42.195 km (26.22 miles). The race buttons fill in these exact distances.
How do I convert pace per mile to pace per kilometre?
Divide the pace per mile by 1.609344, since that is how many kilometres are in a mile. 8:00 per mile is 480 seconds ÷ 1.609344 = 298 seconds, or 4:58 per km. Going the other way, multiply by 1.609344.
How do I turn pace into treadmill speed?
Speed in mph is 60 divided by your pace in minutes per mile. A 10:00 mile is 6.0 mph, a 9:00 mile 6.7 mph and an 8:00 mile 7.5 mph. The calculator shows the speed in mph and km/h with every result.
Should I run even splits?
Even splits, the same pace each mile, are the simplest plan and keep you from going out too fast. The splits table shows the clock time you should see at each mile or kilometre at an even pace. Hills, wind and water stops will move them around a little.