Pace Calculator

A Pace Calculator works out the relationship between how far you go, how long it takes, and how fast you move. Give it any two of those three - distance and time, distance and pace, or time and pace - and it returns the missing value. Enter a 10K and a 55-minute finish, for example, and it tells you that is a 5:30 per kilometre pace (about 8:51 per mile) at 10.9 km/h. It replaces the error-prone mental arithmetic runners, walkers, and cyclists do to plan a session or predict a race.

For a 5K, the split table works as a pace chart for one goal time. Choose Pace, tap the 5K preset and enter 25 minutes: the 5K pace calculator shows 5:00 per km, 8:03 per mile and 12.00 km/h, with splits at 5:00, 10:00, 15:00, 20:00 and 25:00. Switch the distance to mi and the preset becomes 3.11 mi, so the table lists 8:02, 16:05 and 24:07 plus a final 3.11 mi row at 25:00. The table shows one pace at a time. To compare goal times, change the time and read it again.

Pace and speed describe the same thing from opposite directions. Pace is time per unit of distance - minutes per kilometre or per mile - and is how runners usually think, because it maps directly to what a watch shows each split. Speed is distance per unit of time - kilometres or miles per hour - and is how cyclists and treadmills usually label effort. This tool reports both at once, along with the equivalent pace in the unit you did not pick, so a plan written in min/km is instantly readable by someone who trains in min/mile.

Everything is computed in your browser in plain JavaScript. No times, distances, or training data are uploaded or stored, there is no sign-up, and the calculator keeps working with no connection once the page has loaded - useful at a start line or on a track with poor signal. It is built to be quick on a phone but works equally well on a laptop for planning a training block or a goal race.