Race Day Fueling Calculator

How it is calculated

The tool turns an hourly carbohydrate target into a total and a per-quarter-hour dose. total (g) = carbs per hour × race hours and per 15 min (g) = carbs per hour ÷ 4. The rate is in grams of carbohydrate per hour and the duration in hours, as a decimal: 3 h 30 min is 3.5. The total is rounded to whole grams and the 15-minute dose to one decimal. The tool does not judge whether the rate is sensible for the gut or the event and does not read the carbohydrate content of products, so you convert gels or drinks to grams yourself. A rate of zero is accepted, while a duration of zero or less, or a negative rate, gives no result. A time such as 3:30 is not understood.

Common mistakes

• Typing the race time as 3:30 or 3.30. A colon is not accepted, and 3.30 means 3.3 hours (3 h 18 min), not three and a half hours. Use 3.5.
• Entering the grams of product instead of grams of carbohydrate. A 40 g gel pack usually holds less than 40 g of carbohydrate, so read the carbohydrate line.
• Using a rate you have never practised. The hourly target is only a planning input; gut tolerance has to be trained before race day.
• Carrying exactly the calculated total. Add a margin for a slower finish or dropped items; the total is what you plan to eat, not what you should carry.
• Forgetting to account for the carbohydrate in the sports drink you plan to sip. It counts toward the hourly target, so do not add gels on top of it.