London Marathon 3:45 pace chart

A 3:45:00 marathon is 8:35 per mile or 5:20 per kilometre held for the full 26.2 miles (42.195 km). On the London Marathon specifically, the elevation profile means even effort produces uneven splits — the table on this page gives the target for every kilometre.

1:52:08. That is the grade-adjusted halfway target for this course, not simply half of 3:45:00 — it accounts for where the climbing sits. Reaching the half meaningfully faster than this on this course usually means you have spent the effort you need for the closing miles.

Even effort at a 3:45 goal produces splits between 4:35 and 5:31 per kilometre — about 56 seconds between the easiest and hardest one. Grade-adjusted pacing gives back time on the descents and spends it on the climbs, which is what running an even physiological effort actually looks like on a course with this profile.

Each kilometre is weighted by its gradient using the Minetti et al. (2002) cost-of-running polynomial, which measures the metabolic cost of running at grades from −45% to +45%. The total is then scaled so the whole course adds up to 3:45:00. Uphill sections get more time and downhill sections less, at a constant effort throughout.

3:45 is a fast recreational time, roughly the top quintile of a big-city field. Whether it is realistic for you depends on your recent race results and weekly volume rather than on the number itself — the race-time predictor on this site will convert a recent 5K, 10K or half-marathon result into a marathon estimate using the Riegel power-law model.