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Pace Calculator

Work out your running pace, finish time or distance, and see the split times for each kilometre or mile.

Maintained by BrowserTools · Last updated 2026-09-29

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Pace is the number runners actually think in: how many minutes and seconds each kilometre or mile takes. This calculator links the three values that describe any run, distance, time and pace, and solves whichever one you leave out. Enter a distance and a finish time to see the pace you need, a distance and a pace to see your finish time, or a time and a pace to see how far you would go. Distances work in kilometres or miles, pace can be typed per kilometre or per mile, and every result is shown in both systems at once, together with speed in km/h and mph and the equivalent time for a 400 metre track lap, so the numbers are useful whether you train on roads in Europe, trails in the United States or a running track anywhere.

Frequently asked questions

How is running pace calculated?
Pace is time divided by distance. A 10 km run in 50 minutes is 50 ÷ 10 = 5 minutes per kilometre, written 5:00 /km. To get pace per mile, divide by the distance in miles instead (10 km is 6.214 miles), which gives 8:03 /mile. Speed is the inverse: distance divided by time, so the same run is 12 km/h or 7.46 mph.
What finish time does a 5:00 per km pace give for a marathon?
A marathon is 42.195 km, so 42.195 × 5 minutes = 210.975 minutes, which is 3 hours 30 minutes and 59 seconds (3:30:59). At the same pace a half marathon takes about 1:45:29, a 10K 50:00 and a 5K 25:00.
How do I convert pace per km to pace per mile?
Multiply the pace per kilometre by 1.609344, the number of kilometres in a mile. For example 5:00 /km is 300 seconds, and 300 × 1.609344 = 482.8 seconds, or 8:03 /mile. To go the other way, divide the pace per mile by 1.609344. The calculator shows both at once so you do not need to convert by hand.
What is a negative split?
Running a negative split means covering the second half of a race faster than the first. Many coaches recommend it because starting slightly conservatively saves energy for the end. In this tool, a negative split of 2% makes the second half pace 2% quicker than the first half pace while keeping your total finish time the same, and the split table shows the resulting time for every kilometre or mile.
How accurate is the race time predictor?
It uses the Riegel formula, T2 = T1 × (D2 / D1)^1.06, which describes how pace slows as distance grows. It works best between distances that are not too far apart and assumes equal training for both. Predictions from short races to the marathon are often a few minutes too fast, because the marathon also depends on long run training, fuelling and weather. Treat it as a starting point for a goal, not a guarantee.
What is the 400 m lap time for?
A standard outdoor running track is 400 metres per lap in lane one, so the lap time is how long each lap should take at your pace. It is handy for interval sessions and for checking pace without GPS, which can be inaccurate on a tight track. Remember that outer lanes are longer, lane eight adds about 54 metres per lap.
How do I type the time?
Use hours, minutes and seconds separated by colons, like 1:45:30 for one hour, 45 minutes and 30 seconds, or minutes and seconds like 25:00. Pace uses minutes and seconds, such as 5:30. A single number without colons is read as minutes, so 90 means 1:30:00.
Why is the half marathon 21.0975 km?
The marathon distance was fixed at 42.195 km (26 miles 385 yards) in 1921, based on the course of the 1908 London Olympics, and a half marathon is exactly half of it. The presets use these exact values, since rounding the marathon to 42 km would make your planned finish time about a minute too fast at a typical pace.

About Pace Calculator

The race presets fill in the standard distances exactly: 5 km, 10 km, the half marathon at 21.0975 km and the marathon at 42.195 km. Those odd decimals matter, because a marathon planned as 42 km comes out about a minute short at a typical pace. Below the results, a split table lists the time for every kilometre or mile plus the final partial segment, with the elapsed time at each marker, which is what you want to write on a wristband or check against your watch. If you plan to run the second half faster, set a negative split percentage and the table spreads the same finish time over a slower first half and a quicker second half. The table can be copied straight into a spreadsheet or downloaded as a CSV file.

The race time predictor takes the run you entered and projects it to other distances with the Riegel formula, T2 = T1 × (D2 / D1)^1.06, published by Peter Riegel in 1977 and still the most common rule of thumb. It is a useful way to set a realistic goal, for example turning a recent 10K into a target half marathon time, but it is only an estimate: it assumes you have done the training for the longer distance, and many runners find it optimistic for the marathon, where fuelling and endurance count for more. Time fields accept h:mm:ss or mm:ss, and everything is calculated in your browser.

Why the marathon is 42.195 km

The first modern marathon, at the 1896 Athens Olympics, was about 40 km, inspired by the legend of a messenger running from the battlefield of Marathon to Athens. For the next few Games the distance varied with the course.

At the 1908 London Olympics the route was laid out from Windsor Castle to the stadium at White City, and the finish was placed in front of the royal box. That produced a course of 26 miles and 385 yards, or 42.195 km. After years of different lengths, the International Amateur Athletic Federation adopted that figure as the official distance in 1921.

The 1908 race also gave the event one of its most famous moments: the Italian runner Dorando Pietri entered the stadium first but collapsed several times and was helped over the line by officials, which got him disqualified. Queen Alexandra later presented him with a gilded silver cup for his effort.

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