Running Pace Calculator
Pace, time, distance — enter any two, the third appears. Presets for 5K, 10K, the half and the exact 42.195 km marathon, pace shown per kilometre and per mile, and kilometre splits you can pace a race from.
One equation, three questions
Time equals pace times distance. Every training question — how fast must I run, when do I finish, how far did I go — is that identity solved for a different unknown, which is why the calculator asks for any two and refuses to ask for more.
The one subtlety is units: pace is time per distance, so 5:30 is five minutes thirty seconds, not five point three. Everything here parses and prints clock format for exactly that reason, and the per-mile line is the same pace in the other convention rather than a second calculation.
Frequently asked questions
What pace do I need for a 4-hour marathon?
5:41 per kilometre — 42.195 km divided into 240 minutes. The same arithmetic answers every such goal: a 50-minute 10K is 5:00/km, a 2-hour half is 5:41/km too. Enter the goal time with the race preset and read the pace line.
Why does the marathon preset say 42.195 and not 42.2?
Because the missing 5 metres are 1.7 seconds at 5:41/km — and race plans fail on accumulated roundings. The distance has been exactly 42.195 km since 1921; a pace band computed on 42.2 has you arriving late by the length of the finishing straight's error.
What are the splits for?
Even pacing is the single most reliable racing strategy, and the splits table is what it looks like on a watch: the elapsed time you should see at each kilometre marker. Ahead of the number means you went out too fast — the marathon collects that debt with interest after kilometre 30.
How do pace and speed relate?
They are reciprocals: 5:00/km is 12 km/h, 6:00/km is 10 km/h. Runners think in pace because watches show it and race maths adds it linearly; treadmills insist on km/h — the speed line exists so you can set the belt to match your target pace.
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