How it works
required pace = goal time ÷ 26.2188 mi (or ÷ 42.195 km)
Average pace is elapsed time divided by distance — the kinematic definition of speed, expressed as time per unit. For a marathon the distance is fixed at exactly 42,195 m (26 miles 385 yards, World Athletics standard), so the only variable is your goal time. We compute everything in SI units (metres and seconds) internally and convert to miles or kilometres only at the display edge, so both unit views are always consistent (ADR-9). The halfway split assumes perfectly even pacing — in practice most runners aim for a slight negative split, but even pace is the simplest feasible target. The marathon is the one distance where the even-pace number is a starting point, not a guarantee: glycogen runs low somewhere past 30 km, and a start even a few seconds per mile too fast is what turns the final 10 km into the wall and a heavy positive-split fade.
Sources
- Marathon distance — World Athletics standard World Athletics (formerly IAAF) — the marathon is defined as exactly 42.195 km (26 miles 385 yards).
- Definition of average pace Average speed = distance ÷ time (kinematics); pace is its inverse, expressed as time per unit distance. Halliday, Resnick & Krane, "Physics", 4th ed., §2-2.
- Why even pace is the physiological optimum Riegel, P. S. (1981). "Athletic Records and Human Endurance." American Scientist 69(3), 285–290. Even-pace or slight negative-split strategies minimise energy cost over long events.
FAQ
What pace do I need to run a sub-4 hour marathon?
To finish a marathon in under 4:00:00 you must average faster than 9:09 per mile (5:41 per km). That works out to a half-marathon split of 1:59:59 or better on even pace.
What pace do I need for a sub-3:30 marathon?
A 3:30:00 marathon requires holding 8:01 per mile (4:59 per km). At even pace your halfway split is 1:45:00. Most runners find it easier to hit 1:44–1:45 at the half and negative-split the second half.
What pace do I need for a sub-3 hour marathon?
Under 3 hours means averaging faster than 6:52 per mile (4:16 per km) — a halfway split of 1:30:00 or quicker. This is an elite-amateur level requiring substantial base mileage and speed work.
Is even-pace realistic for a marathon?
Even pace is the mathematical ideal and the simplest target, but most runners slow in the second half due to glycogen depletion and accumulated fatigue. Aim to run 1–2 % slower in the first half (a slight positive split) or bank a few seconds per mile early and negative-split — both strategies have helped elite marathoners set PRs.
Should I track marathon pace in miles or kilometres?
Match your course markers, but know the gap: a sub-4:00 marathon is 9:09 per mile yet 5:41 per km, and over 26.2 miles a small per-unit drift snowballs into minutes — exactly the early over-pacing that triggers a late fade. The calculator shows both figures plus the halfway split so a kilometre-marked course and a mile-based watch agree from the start line to the finish.
How does the per-400 m time help marathon training?
A standard track lap is 400 m, so the per-400 m figure is your goal lap time at marathon effort. Marathon pace can feel deceptively easy on fresh legs, so use this lap time for long marathon-pace blocks — 6 to 16 km at goal effort — to rehearse holding it as fatigue builds, the rehearsal that keeps you off the wall when glycogen drops in the closing miles.
How accurate is the halfway split?
The split assumes perfectly even pace across the full 42.195 km. Real courses vary by elevation and weather, and fatigue typically slows the second half. Use it as your even-pace ceiling and factor in 30–90 seconds of cushion for a realistic race plan.
Pace figures are mathematically exact for the goal time you enter. The halfway split assumes perfectly even pace and is not a personalised prediction. General information for planning purposes only — not medical, coaching, or race-strategy advice.