Marathon Fueling Plan Calculator

Build a marathon fueling plan in minutes. Calculate carbs per hour, total carbs, gels needed, and a simple timing schedule to avoid hitting the wall.

Use your target finish time to estimate how many gels you need and when to take them, with realistic 60-90g/hr carb targets.

Carbs/hour target + total carbs
Gel count estimate
Simple race-day timing guidance

How to build a marathon fueling plan

Enter your marathon finish time and preferences to get a gel count estimate and carb targets.

Enter finish time: Use your realistic goal time or recent marathon result.
Choose race type: Select Marathon to apply marathon-specific guidance.
Generate the plan: Get carbs/hour, total carbs, and gels needed.

Frequently asked questions

How many carbs per hour for a marathon?

Most runners do well in the 60-90g/hour range, depending on gut training, intensity, and product tolerance.

When should I take my first gel?

Many runners start early (around 20-30 minutes) to stay ahead of energy needs, then follow a steady schedule.

Fueling reference

Race-day carb targets and gel counts by finish time (baseline, no body weight entered)
Race	Finish time	Carbs/hour	Total carbs	Calories	Gels
Half marathon	1:20	45 g/hr	60 g	240 kcal	2
Half marathon	1:35	45 g/hr	71 g	284 kcal	3
Half marathon	1:50	45 g/hr	83 g	332 kcal	3
Half marathon	2:05	45 g/hr	94 g	376 kcal	4
Half marathon	2:20	45 g/hr	105 g	420 kcal	4
Marathon	2:50	75 g/hr	213 g	852 kcal	5
Marathon	3:15	75 g/hr	244 g	976 kcal	5
Marathon	3:45	75 g/hr	281 g	1124 kcal	6
Marathon	4:15	75 g/hr	319 g	1276 kcal	7
Marathon	4:45	75 g/hr	356 g	1424 kcal	7
Marathon	5:15	75 g/hr	394 g	1576 kcal	7

Method and sources

The numbers on this page are computed with the same code as the TrainPace calculators, from these published methods. They are training guidance, not medical advice.

Jeukendrup, A. (2014). A step towards personalized sports nutrition: carbohydrate intake during exercise. Sports Medicine 44(Suppl 1), S25–S33 — carbohydrate targets by event duration, and glucose + fructose for intakes above 60 g/hr.
Thomas, D.T., Erdman, K.A. & Burke, L.M. (2016). Nutrition and Athletic Performance (joint position statement of the ACSM, Academy of Nutrition and Dietetics, and Dietitians of Canada). Medicine & Science in Sports & Exercise 48(3), 543–568.

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Every public page on this site has a Markdown mirror at the same path with a .md suffix (for example /calculator.md), and honors an Accept: text/markdown request header on the HTML URL. The calculations here are also available as callable tools through a free public MCP server — no account or API key.