Pace in, time out
This is the reverse of the pace calculator, and the plainest kind of run time calculator: you know the pace you can hold and want to know what it gives you. A 5:30 per kilometre pace over a half marathon is 1:56:02, which is the kind of number that decides whether a goal is realistic before you enter a race.
Mixing units safely
Distance and pace can be entered in different units — 26.2 miles at 5:30 per kilometre is a valid question, and the calculator handles it without silently mixing them. That matters because a plan written in miles and a watch set to kilometres is a common combination.
What the number does not include
Even pacing is assumed. Real races include water stations, hills and crowds, which typically add 1–3%. For a marathon, add 3–5 minutes to the arithmetic if you have not raced the distance before; the race predictor gives a more honest estimate from a recent result.
Frequently Asked Questions
Why is my actual time slower than this?
The calculation is exact for the pace you enter. If you slowed down in the second half, your average pace was slower than the pace you started at.
Can I use 4:30 per mile?
Yes, enter 4:30 and choose per mile. The result shows both the finish time and the metric pace.
Does it work for swimming?
The arithmetic does, but swim pace is normally given per 100 m. Use the swim pace calculator instead.
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Privacy & your data
SwimRunPace calculates everything in your browser. Distances, times and body weights are never uploaded — there is no account, no server-side record and no training history stored between visits.