From goal to pace
A 3:30 marathon is 4:59 per kilometre, or 8:00 per mile. Those two numbers are the whole race plan: every checkpoint on the course should show the elapsed time in the table if you are on schedule. The halfway split is simply half the goal time, which makes the 21.1 km marker the most useful reality check on the day.
Why even pacing wins
Running the first half too fast is the most common marathon mistake. Every 5 seconds per kilometre you bank early costs roughly 10–15 seconds per kilometre later, because glycogen depletion is not linear. The table's 2% negative split figure shows what a slightly conservative first half looks like.
Course and conditions
A hilly course adds 1–3 minutes; 20°C and above adds 2–5% for most runners. Neither is in the arithmetic here, so treat the checkpoint times as a flat, cool-day target and adjust before the start rather than at 30 km.
Frequently Asked Questions
What pace is a sub-4 marathon?
4:00:00 is 5:41 per kilometre or 9:09 per mile. A sub-3:30 is 4:59 per kilometre.
Should I run even splits?
Yes, for most runners. A slight negative split — 1–2% slower in the first half — is even better, but even pacing is far safer than a fast start.
Does the calculator include walk breaks?
No. If you plan to use run/walk, the Galloway calculator accounts for the walking segments.
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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.