What is the official marathon distance?

A marathon is 42.195 kilometres, about 26.22 miles. The tool uses that exact distance so the per-km and per-mile pace and the 5K checkpoint splits are correct.

What is the wall-aware pacing plan?

It models the common slowdown after 30 km by assuming the final 12.195 km run about 4% slower than average. The tool then solves the slightly faster even pace you need for the first 30 km so the total still meets your goal time.

Why pace the first 30 km carefully?

Most positive splits in marathons come from going out faster than the first-30 km target. Banking time early feels easy but the wall amplifies any over-effort, so disciplined early pacing is the single biggest protector of your finish time.

How accurate is the 4% fade assumption?

It is a reasonable average for well-trained amateurs; elites fade less and undertrained runners fade more. Treat the wall-aware split as a planning guide and adjust the early pace if your long runs suggest a smaller or larger drop-off.

What are the 5K checkpoints for?

They give the cumulative clock time you should see at every 5 km on even pace, matching most course markers. Comparing your watch to each checkpoint tells you immediately whether you are on, ahead of, or behind goal pace.

Marathon Pace Calculator

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The marathon punishes pacing errors more than any other common distance because the wall magnifies every fast early kilometre. A precise goal pace, 5K checkpoints, and a plan that anticipates the late-race fade give you the best chance of an even, well-judged finish.

How it works

The marathon distance is fixed at 42.195 km. Even-pace figures are direct, and the wall-aware plan back-solves the early pace:

pace per km   = totalSeconds / 42.195
pace per mile = totalSeconds / 26.2188
checkpoints   = pace per km × {5,10,15,20,25,30,35,40,42.195}

# wall-aware: final 12.195 km run 4% slower
earlyPace = total / (30 + 1.04 × 12.195)
latePace  = earlyPace × 1.04

The early pace is therefore slightly faster than the flat average, so the planned late slowdown still lands you on your goal time.

Example and tips

For a 3:45:00 goal, the even pace is about 5:20 per km (around 8:35 per mile) with the 30 km checkpoint near 2:40:00. The wall-aware plan asks for a marginally faster first 30 km and allows a controlled fade afterward. The biggest single mistake is starting faster than the first-30 km figure, so hold back early and let the plan carry you home.