How do you pace a marathon?
Pick a goal pace your training supports, run the first 5 km at or a little slower than it, hold even effort through halfway, and only race from about 30 km.
Marathon pacing starts before race day, with the goal. The pace has to come from evidence — a recent half marathon converted with a race predictor, checked against your long runs and weekly volume — rather than from a round number you would like to break. A goal your training does not support cannot be rescued by pacing; a realistic one is very hard to ruin if you pace it sensibly.
On the day, the first 5 km is where most marathons are lost. Adrenaline, a taper and a crowd make goal pace feel effortless, and running 10–15 seconds per kilometre faster than planned feels like banking time. It is not: the energy cost of running fast early is paid back with interest after 30 km, and studies of big-city fields find slower runners tend to slow the most in the second half. Aim to reach 5 km at goal pace or a few seconds per kilometre slower, and accept that congestion may make it slower still.
From there, hold even effort rather than chasing the watch. On a flat course even effort and even pace are almost the same thing, and the target at halfway is simply half your goal time, give or take a minute. On a hilly course, let pace slow on climbs and recover on descents, and use a grade-adjusted split table to know what each section should cost. Heat matters too: finishing times slow progressively as conditions warm above roughly 10 °C, and slower runners lose proportionally more, so on a warm day the right move is to lower the goal at the start rather than discover it at 30 km.
The race proper begins around 30–32 km. If you are still at goal effort and fuelling has gone to plan, this is where you can press. If you are already struggling, holding pace — not making up time — is the win. Two practical details help throughout: your watch will drift long because nobody runs the measured line perfectly, so trust the kilometre or mile markers, and a pace group running your goal time takes the arithmetic off your hands, provided it is not going out faster than advertised.
Key numbers
| First 5 km | goal pace or a little slower | never meaningfully faster |
|---|---|---|
| Halfway target | half the goal time | flat course; ±1 minute |
| Start racing | ~30–32 km | if effort and fuelling allow |
| GPS drift | reads long | trust the course markers |
Work it out for yourself
HR pacing simulator — See how starting pace, heat and cardiac drift play out over the full distance before you race it.
Frequently asked questions
Should I run even splits or negative splits in a marathon?
On a flat course, aim for even effort with a first half a shade slower than the second, which lands close to even overall. A deliberately negative split often means a first half so conservative that the time is lost rather than banked.
How fast should the first mile of a marathon be?
At goal pace or slightly slower — a few seconds per mile is fine. A first mile well under goal pace is the most common pacing error in the marathon, and it rarely feels like a mistake until the last 10 km.
Should I pace a marathon by heart rate or by pace?
Use pace as the target and heart rate as the warning light. Heart rate drifts upward over a marathon even at constant pace, so holding a fixed heart rate means slowing steadily; but a heart rate well above your usual marathon effort in the first hour is a reliable sign you have started too fast.
Should I run with a pace group?
Usually yes, if one runs your goal time. It removes the arithmetic and the temptation to surge. Stay with it through halfway, check it is not running faster than its sign, and decide after 30 km whether to move ahead.
How should I adjust my marathon pace for heat?
Lower the goal before the start rather than finding out at 30 km. Performance slows progressively as it warms above roughly 10 °C, and slower runners — who are out longer — lose proportionally more.
Sources
- Abbiss & Laursen (2008). Describing and understanding pacing strategies during athletic competition. Sports Medicine.
- Ely, Cheuvront, Roberts & Montain (2007). Impact of weather on marathon-running performance. Medicine & Science in Sports & Exercise.
- Santos-Lozano et al. (2014). Influence of sex and level on marathon pacing strategy. Insights from the New York City race. International Journal of Sports Medicine.
Related explainers
Glossary: Riegel Model