Carbs Per Hour for Running

Carbs per hour running calculator. Estimate a realistic carb target for marathon or half marathon fueling (60-90g/hr) based on your finish time.

Carbs/hour is the simplest "fueling dial" you can turn. The right target depends on duration, intensity, and gut training.

60-90g/hr targets (adjustable)
Total carbs + gel estimate
Practical, race-day friendly guidance

How to choose carbs per hour for a race

Estimate a carbs-per-hour target and convert it into gels and timing.

Choose race duration: Longer races typically benefit from more consistent fueling.
Pick a target range: Start with 60g/hr and progress toward 90g/hr if tolerated.
Practice in training: Use long runs to train your gut and confirm products.

Frequently asked questions

Is 90g/hr too much?

For some runners, yes. For others (with gut training and proper products), it's very doable. Start lower and practice.

Does body weight change carb needs?

Weight matters less than duration and intensity for carbs/hour. Tolerance and practice matter most.

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

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Every 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.