Marathon fueling
Marathon fueling plan, built around your pace and course
Splitshape plans your race-day fueling inside your pacing plan: when to take each gel, how much, and how many to carry, placed on your own splits for your course and forecast. Plus a carb loading guide for the days before.
Why fueling decides the second half
Pacing decides how fast you spend your energy. Fueling decides how much you have left to spend after km 30, when the pace that felt easy starts to cost more.
I learned this the hard way. In one marathon, poor fueling on the course and too little carb loading before it cost me my legs late in the race, and no pacing plan could fix that. So Splitshape plans both, in one place.
The hard part isn't knowing that you need carbs. It's knowing when to take them on your course, how many to carry, and how much your stomach handles at race pace. That's what the plan works out.
What your Splitshape fueling plan includes
A gel schedule on your splits
Every gel sits at a km or mile marker, with the time from the start, the grams and whether to wash it down with water. Nothing in the first 30 minutes, nothing in the last 20.
A carbs-per-hour target you choose
Pick how used your gut is to gels, from 40 to 90 g of carbs per hour. The schedule is built to stay within that target.
Your own gel
Enter the carbs per gel and whether it needs water or contains fructose. Above 60 g per hour, the plan tells you when a glucose-only gel is a poor fit.
How many gels to carry
The plan counts the gels for the course plus the optional one before the start, so you know what goes in your pockets.
Optional caffeine
Switch on caffeinated gels for the second half. They stay within a caffeine limit based on your body weight, or a fixed limit if you don't enter it. Your body weight is saved only on your device.
A carb loading guide
For a race over 90 minutes: 10–12 g of carbs per kg of body weight a day for the last 36–48 hours, and a pre-race meal of 1–4 g per kg, 1–4 hours before the start. Shorter races get a lighter guide for the last 24 hours. Amounts and timing, not a meal plan.
Gels in your exports
Gel stops appear on the printable pace band, in the Garmin course waypoints and in the CSV, and on the lock-screen card when they fit.
A short strategy note
An AI-written note explains why the gels sit where they do. Its numbers are checked against the schedule, and the schedule itself is calculated, not written by AI.
A real gel schedule
How it works
Pick your course
Choose one of 38 races or upload any GPX file.
Set your goal
Enter your target time and a recent result. Splitshape builds your pacing plan for your course and the race-day forecast.
Set your fueling
On your plan, choose how many carbs per hour your gut handles and enter your gel. The gel schedule and the carb loading guide update right away.
Fueling and pace belong in one plan
A gel every 30 minutes by the clock ignores the course. Your Splitshape plan places each gel by kilometre on your actual course, using the same weather-adjusted splits as your pace band.
If a gel would land right before a climb, it moves to an earlier marker, so you're not taking a gel as the road goes up. If heat or a headwind slows your splits, the gels move with them. On a warm or humid day, the plan reminds you to wash every gel down with water.
When you refresh your plan with the latest forecast before race day, the gel schedule is recalculated with it.
Marathon fueling FAQ
Does Splitshape include a marathon fueling plan?
Yes. Every plan includes a gel schedule timed to your own splits: when to take each gel, how much, and how many to carry. You set how many carbs per hour your gut is used to (40–90 g) and enter the gel you train with. There's also a carb loading guide for the days before the race.
How many gels do I need for a marathon?
It depends on your finish time, the carbs in each gel and how many carbs per hour your gut handles. With the default settings (60 g per hour, 25 g gels), a 3:00 to 5:00 marathon gets 5 to 10 gels on the course, plus an optional one before the start. Your plan works out the exact number from your predicted finish on your course and your own gel.
What is carb loading, and does Splitshape plan it?
Carb loading means eating more carbohydrate than usual in the last days before a race, so you start with your glycogen stores topped up. For a race longer than 90 minutes your plan gives 10–12 g of carbs per kg of body weight a day for the last 36–48 hours, plus a pre-race meal of 1–4 g per kg, 1–4 hours before the start. Add your body weight and it shows the amounts in grams. It gives amounts and timing, not a meal plan.
Can I use my own gels?
Yes. Enter the carbs per gel and whether it needs water or contains fructose, and the schedule is built around that gel. If your gel also comes in a caffeinated version, you can use it for the second half, capped by a caffeine limit.
When should I take my first gel in a marathon?
In your Splitshape plan the first gel on the course comes about 35 minutes in, never in the first 30 minutes, on the nearest km or mile marker. An optional gel 12 minutes before the start comes on top. In the Frankfurt sample plan, that puts the first gel at km 8.
Does the fueling plan work for a half marathon?
Yes. The schedule is based on your predicted finish time, not the distance. Under 75 minutes the plan tells you that no gel is needed during the race; from 75 minutes on you get at least one. For races under 90 minutes, carb loading switches to a lighter guide for the last 24 hours.
Is this medical or dietitian advice?
No. Pacing and fueling plans are general guidance for healthy adults, not medical, dietitian or coaching advice. Practise your fueling in training and adjust it to your own tolerance.
Build your pacing and fueling plan
Pick your race, set your goal, and get one plan for pace, weather, terrain and fuel.
Build my FREE plan →Pacing and fueling plans are general guidance for healthy adults, not medical, dietitian or coaching advice. Practise your fueling in training and adjust it to your own tolerance.