Curated by Vinod Kumar Jain & Amit Jain · All Frontier Global · free, no login
Give any two of distance, time and pace and this returns the third, plus what that pace means over the standard race distances and at each kilometre and mile. Plain arithmetic on fixed distances — no training plan, no fitness model, no predictions about what you could run on the day.
The arithmetic
Pace = time ÷ distance · Time = pace × distance · Distance = time ÷ pace
Speed = distance ÷ time, shown in km/h and mph alongside the pace.
Standard distances are fixed: 5K and 10K exactly, half marathon 21.0975 km, marathon 42.195 km. Miles convert at 1 mile = 1.609344 km.
Split times assume an even pace throughout, which is a modelling choice rather than a prediction.
Honest limits
This is arithmetic, not coaching. The shell this page replaced offered weekly pace targets from “current fitness and weeks until race”. That needs a training model and knowledge of you; there is none here and none pretended.
Even splits are an assumption. Real races are not run at constant pace — terrain, wind, heat, crowding and fatigue all move it, and most positive splits arrive in the last quarter.
Nothing here predicts a race time from a shorter one. Equivalent-performance formulas exist and are not used, because they assume training specificity this tool knows nothing about.
No physiology, no heart-rate zones, no effort model. Distance divided by time, and back again.
Sources
None needed: the only constants are the fixed race distances — 21.0975 km for a half marathon, 42.195 km for a marathon — and the mile, defined as exactly 1.609344 km. Everything else is your own input.