Running Pace Calculator

Can I enter pace and get a time or a distance?

No. Although the tool is described as solving for any one of three values, this calculator takes a distance in kilometres and a finish time, and returns the pace. To find a time for a given pace, enter the distance and a trial time and adjust until the pace matches.

How are pace, mile pace and speed computed?

Pace per km is your total time in seconds divided by the distance in km, shown as minutes and seconds. Pace per mile multiplies the seconds per km by 1.60934. Speed is 3600 divided by seconds per km for km/h, and that value divided by 1.60934 for mph.

How are the 5K, 10K, half and marathon times projected?

The code multiplies your pace by each distance (5, 10, 21.0975 and 42.195 km) and assumes you hold exactly that pace throughout. There is no fatigue adjustment, so the marathon figure is the time you would run if an easy 5K pace never slowed, which few people achieve.

Can I enter miles?

The distance box is in kilometres only. To use a distance in miles, multiply by 1.60934 first; for example, 6 miles is 9.66 km. The mile pace in the results is just the km pace converted.

Can seconds exceed 59, and what counts as invalid?

Seconds above 59 are simply added: 25 minutes and 90 seconds is 26:30. A distance of zero or less, or a total time of zero or less, returns an error message. Pace and projections are rounded to whole seconds after the calculation, so a result never displays as something like 5:60.

Do small rounding differences matter?

Slightly. Pace is rounded to the nearest second per km, but projections are calculated from the unrounded pace, so a half marathon may differ by a second from 21.0975 times the displayed pace. For race planning, those seconds are negligible.

Does the result account for hills, heat or my fitness?

No. It is pure arithmetic on the time and distance you enter, so a hilly run gives a slower pace and any projection assumes flat, steady conditions.