How Pace Ladder calculates pace

Pace = time ÷ distance. A 1:20:00 half marathon is 4,800 seconds ÷ 21.0975 km = 227.52 seconds per km, which is 3:48/km, or 6:06/mi.

Speed is the other way round: speed = distance ÷ time. The same race is 21.0975 km ÷ 1.3333 hours = 15.8 km/h, or 9.8 mph.

min/km = 60 ÷ km/h, and min/mi = 60 ÷ mph. 12 km/h is 5:00/km; 6 mph is 10:00/mi.

To turn min/km into min/mi, multiply by 1.609344. 5:00/km is 8:03/mi.

Paces are shown rounded to the nearest second, so 227.52 seconds per km is shown as 3:48, not 3:47. Speeds are shown to one decimal place.

Rounding is for display only: every calculation uses the unrounded values. Finish times, splits and elapsed times are also shown to the nearest second, so a column of splits can differ from the finish time by a second.

T2 = T1 × (D2 ÷ D1)^1.06, where T1 is a time you ran over distance D1 and T2 is the estimate for distance D2.

For example, a 1:20:00 half marathon gives 4,800 × (42.195 ÷ 21.0975)^1.06 = 4,800 × 2.0849 = 10,008 seconds: a 2:46:48 marathon.

It’s an estimate. It assumes you’ve trained for the other distance, and it knows nothing about heat, hills or how your long runs went.

Even splits give every km or mile the same pace. A negative split of a given percentage makes the second half that much quicker than the first, with the same finish time.

The last split covers whatever distance is left over: 0.195 km in a marathon, 0.0975 km in a half.

Times, paces and speeds can be typed the way you’d write them: 3:30, 1:20:00, 1h20, 4.5, 15 km/h or 6:06/mi.