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Marathon pace: choose it right, hold it to the end

More marathons are ruined by the first 10 kilometres than by the last 10. Go out 10 seconds per kilometre too fast and you don't lose 10 seconds — you lose 10 minutes, somewhere after kilometre 30. Pacing is the one race skill that costs nothing and pays enormously. Here's how to choose a target you can actually hold, and how to run it.

Why marathon pacing is unforgiving

The marathon is the only popular distance run right at the edge of your glycogen reserves. Run at a sustainable pace and your body burns a manageable mix of carbohydrate and fat for four hours. Run even slightly too fast and you burn carbohydrate disproportionately faster — until the tank empties around kilometre 30–35. That's the wall, and it isn't a myth: it's arithmetic. The fix isn't more willpower late in the race; it's more discipline early.

Choosing a realistic target

Your marathon pace should be derived from evidence, not ambition. Two reliable methods:

  • From a recent half marathon — multiply your half time by roughly 2.08 to 2.10 (Riegel's formula). A 1:50 half predicts about a 3:50 marathon, assuming proper marathon training volume.
  • From pace feel — marathon pace is typically 15–20 seconds per kilometre slower than your half marathon pace, and should feel “comfortably brisk” for the first hour: you can speak in short sentences, not paragraphs.

The prediction only holds if the long runs are in the bank. A great 10K time with a 40 km training week predicts a great 10K — not a great marathon.

The numbers for every goal

Common targets and the pace they require: sub-3h00 means 4:16 min/km, sub-3h30 means 4:59 min/km, sub-4h00 means 5:41 min/km, and sub-4h30 means 6:24 min/km. Each pace table below gives the full kilometre-by-kilometre splits, halfway time included:

Marathon in 4h00 — full pace table
Marathon in 3h30 — full pace table

Executing on race day

  1. 1

    First 10 km: deliberately held back

    Run 5–10 seconds per km slower than goal pace. It should feel almost frustratingly easy. Every second saved here is repaid with interest after kilometre 30.

  2. 2

    10 to 30 km: settle at goal pace

    Lock onto your target and stop looking at the watch every minute. Check your split each 5 km against the pace table you memorised — or wrote on your arm.

  3. 3

    Last 12 km: race what's left

    If the early pacing was honest, this is where you pass people. Negative splitting — running the second half slightly faster — is how most marathon PBs are actually set.

What about hills?

Even pace is the right strategy on a flat course — but on a hilly one, even effort beats even pace. Slowing appropriately uphill and letting gravity give the time back downhill is measurably cheaper than forcing constant splits. If your marathon has real elevation, build a grade-adjusted plan from the actual course file:

Build a grade-adjusted pace plan

After the race: check what really happened

Your GPS file tells the true story of your pacing — where the plan held and where it cracked. Compare your kilometre splits against the plan, and you'll know exactly what to fix next time.

Analyse my race splits

FAQ

What pace do I need for a 4-hour marathon?
5:41 min/km (9:09 min/mile), which is 10.55 km/h. Halfway should pass at 2:00:00 — ideally 1–2 minutes slower if you're aiming for a negative split.
Should I run even or negative splits?
Aim for even effort, which usually means a slightly conservative first half and a matching or marginally faster second half. Most world records — and most amateur PBs — are run with a near-even or negative split.
How much slower is marathon pace than half marathon pace?
Typically 15–20 seconds per kilometre for a well-trained runner. If your half pace is 5:20 min/km, a realistic marathon pace is around 5:35–5:40 min/km.
Is it bad to start a marathon too fast?
It's the most expensive mistake in the sport. Banking time doesn't work: minutes gained early at excessive pace cost double later. If in doubt, start slower — the race truly begins at kilometre 30.
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