Marathon pace calculator

How the marathon pace calculator works

Marathon pace is your goal time divided by the distance: 42.195 km for the full marathon, 21.0975 km for the half. Enter your goal and the calculator gives you the pace per kilometre and per mile, a split every 5 km and, if you choose, a negative-split plan. It is part of the free LeCoach running calculators.

Print the splits or write the key ones on your arm. Checking them every 5 km is easier and calmer than reacting to every kilometre.

Marathon pace chart

Paces are rounded to the nearest second. For a sub-3 marathon the exact pace is 4:15.9 per km, so 4:16 per km all the way would finish just over 3:00. Aim for 4:15 or a little faster if the time matters to you.

Half marathon pace chart

A half marathon in a given time is the same pace as a full marathon in twice that time: a 1:45 half and a 3:30 marathon both need 4:59 per km. The difference is that the second half of a marathon is far harder to hold.

Even pace or negative split?

Even pace means the same speed from start to finish. It is the simplest plan and close to the most efficient way to run a fixed distance.

A negative split means running the second half slightly faster than the first. The calculator makes the first half 1 % slower than even pace and the second half faster by the same time. For a 3:30 goal:

• First half: 5:02 per km (8:05 per mile), reaching halfway in 1:46:03.
• Second half: 4:56 per km (7:56 per mile), covering it in 1:43:57.

The idea is to protect yourself from the most common marathon mistake: going out too fast on fresh legs and race-day adrenaline, then slowing badly in the last 10 km. A small negative split builds in a margin. A big one usually means you started too slowly. For a half marathon at 1:45, the same plan is 5:02 per km for the first half and 4:56 for the second.

How to pick a realistic goal

Your goal should come from your recent races and training, not from a round number.

• Use a recent race. A 10K or half marathon result predicts your marathon better than anything else. The race time predictor and the VDOT calculator turn it into a marathon estimate.
• Check it against training. Goal-pace sections in your long runs should feel controlled. If they feel like a race, the goal may be too ambitious.
• Give it time. A marathon build usually takes 16 to 20 weeks; the how long to train calculator shows how many you need from where you are now.

For your easy, tempo and interval paces, use the running pace calculator.

Common mistakes

• Starting too fast. The first 5 km at goal pace feel easy. That is the point: they are supposed to.
• Trusting GPS pace exactly. Watches drift in cities and under trees, and you will run a little further than the measured course on corners. Use the official kilometre markers for your splits.
• Ignoring weather. Heat and humidity slow marathon times. On a warm day, adjust your goal before the start, not at 30 km.
• Not fuelling. A marathon at any pace needs carbs before and during the race. The carb loading calculator helps you plan the days before.
• Changing the plan mid-race on a good feeling. If you feel great at halfway, wait until 30 km before you speed up.

When your pace should change

• Hot or humid days: start slower and accept a slower finish.
• Hilly courses: run by effort on the climbs, not pace, and let the downhills come to you.
• Wind: shelter in a group into a headwind and save energy.
• A bad build: if illness or injury cost you weeks, lower the goal rather than hoping.

LeCoach builds your marathon plan back from race day, with every run written at paces from your own threshold pace.