Race Fueling Calculator
Enter your distance, goal finish time, and expected conditions to estimate how many carbs, how much fluid, and how much sodium you need per hour -- plus roughly how many gels that works out to. Built with Southeast Asia's heat and humidity in mind, where fueling needs typically run higher than generic guidance assumes.
Runs under an hour generally don't need in-race fueling -- this is built for 10K and up.
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Conditions
Enter a distance and goal finish time to see your fueling plan.
Racing somewhere hot? Check the heat & humidity pace adjuster too, and browse races across Southeast Asia.
Frequently asked questions
How many carbs do I need per hour when running?
Commonly cited sports-nutrition guidance is roughly 30-60g of carbohydrate per hour for efforts over an hour, rising toward 60-90g per hour for longer efforts (2.5h+) using multiple carb sources (e.g. glucose + fructose blends), which the gut absorbs faster than one sugar type alone.
How many gels should I bring for a marathon?
It depends on your goal time and each gel's carb content, but a runner targeting ~60g of carbs per hour over a 4-hour marathon needs roughly 240g total -- about 9-10 standard 25g gels, or fewer if some comes from sports drink instead.
Do I need more fluids and sodium in hot, humid conditions?
Yes, meaningfully more -- sweat rate climbs with heat and humidity, so both fluid and sodium losses increase. This matters especially across Southeast Asia, where race-day heat and humidity are routinely higher than the conditions most generic fueling guidance assumes.
Should I try new nutrition on race day?
No -- test your fueling plan (gel brand, timing, sports drink) in training first. Race day is the wrong time to discover a gel upsets your stomach at pace; by then you either abandon the plan or run the risk of a GI problem mid-race.