Work out pace, finish time or distance, with splits and race predictions. Runs on your device.
Pace is time divided by distance, so any one of the three follows from the other two. A 10K in 50:00 is 3,000 seconds over 10 km, which is 300 seconds per km, or 5:00 per km. In miles the page multiplies by 1.609344: 5:00 per km is 8:02.8, shown as 8:03 per mile. Speed is distance divided by time, here 12 km/h or 7.46 mph. To get a finish time, multiply pace by distance: a marathon of 42.195 km at 5:00 per km is 12,658.5 seconds, shown as 3:30:59. To get a distance, divide time by pace: 1:30:00 at 6:00 per km is 5,400 ÷ 360 = 15 km. Seconds are rounded to the nearest whole second only when shown.
The presets are 5K, 10K, the half marathon at 21.0975 km and the marathon at 42.195 km. Choose Custom to type any distance up to 1,000 in kilometres or miles. Distance and pace have separate unit choices, so you can enter a race in miles and read the pace per km, or the reverse. Time takes hours, minutes and seconds, with seconds allowed to have decimals, and a pace takes minutes and seconds. The How this was worked out box repeats each step with your numbers, so you can check the sum by hand. A time or pace of 0, or a custom distance left empty, shows a message under the box instead of a result.
The Splits table lists each kilometre or mile at an even pace, with the elapsed time. For the 10K above that is ten rows of 5:00, ending at 50:00. A marathon has 42 whole kilometres and a last row of 0.195 km, run in 0:59 to finish at 3:30:59. The table stops at 100 rows and says so. The Race predictions table uses Riegel's formula, T2 = T1 × (D2 ÷ D1)^1.06, to estimate your time at the other race distances. From a 10K in 50:00 it gives 23:59 for a 5K, 1:50:19 for a half marathon and 3:50:01 for a marathon. These are predictions, not results.
A Riegel prediction takes one effort and scales it, so it assumes you have trained for the longer distance and race in similar conditions. It is shown only for efforts from 1 km to 100 km. The further the target distance is from your effort, the less one formula can say. Splits assume the same pace from start to finish, while real races have hills, wind and a slower last stretch. The result is an estimate and nothing here is a training plan. Nothing you enter is stored or sent anywhere.
Divide time by distance. A 10K in 50:00 is 3,000 s ÷ 10 km = 300 s per km, which is 5:00 per km. Choose Pace, pick 10K, type 50 minutes and the page shows 5:00 per km, 8:03 per mile, 12.00 km/h and 7.46 mph.
Multiply the pace by 1.609344. 5:00 per km is 300 s × 1.609344 = 482.8 s, which is 8:03 per mile. The page always shows both units, whichever one you enter.
42.195 km × 300 s = 12,658.5 s, shown as 3:30:59. For a half marathon of 21.0975 km the same pace gives 6,329.25 s, shown as 1:45:29. Choose Finish time, pick the race and type the pace.
With Riegel's formula, T2 = T1 × (D2 ÷ D1)^1.06, where T1 and D1 are your effort and D2 is the other race. From a 10K in 50:00 a marathon comes out at 3:50:01. It is a prediction that assumes similar training and conditions, not a result.
Choose Distance, then divide time by pace. 1:30:00 at 6:00 per km is 5,400 s ÷ 360 s per km = 15 km, or 9.32 miles. Distances over 100,000 km are refused with a message.
No. The numbers stay in this tab and are not stored on your device or sent anywhere. Reloading the page puts the 10K example back. The page only counts that a result was shown, without any of your numbers.