Trail Running Fuelling Calculator
Calculate carbs per hour, total calories, and how many gels to carry for any trail run or ultra. Free, instant, no account needed.
Route & Duration
Your Fuelling Plan
How the Carb Target Is Calculated
Based on ACSM's (American College of Sports Medicine) published breakpoint: 60g/hour for efforts up to 2.5 hours, up to 90g/hour for longer efforts. The higher rate is absorbable thanks to multiple-transportable-carbohydrate strategies (mixed glucose + fructose). The gel-equivalent count uses a ~25g-carbs-per-gel reference figure — this varies by product, so treat it as a rough guide.
Frequently Asked Questions
How many carbs per hour should I eat in an ultramarathon?
ACSM's general guidance is 60g/hour for efforts up to 2.5 hours, up to 90g/hour for longer efforts. Some experienced ultra runners push higher (90-120g/hour), but that requires gut training.
Why do you give a range instead of one exact number?
Carbohydrate tolerance varies a lot by individual and training. This calculator gives a starting point based on ACSM's published duration breakpoint — adjust it based on your own gut training.
How many grams of carbs are in a gel?
It varies by product, but most energy gels carry roughly 20-27g of carbohydrate. This calculator uses a ~25g reference figure to estimate a gel count.
Does elevation gain change my carb needs?
The carb target is driven directly by duration, not elevation — but more climbing usually means a longer duration, which indirectly raises your total carb needs.