Running Fuel & Hydration Calculator

On runs over 60 minutes. Below that, your body has enough stored energy to get through without any extra carbs. Once you pass the hour mark, taking in carbs helps keep your energy steady and stops you from hitting a wall later on.

For most recreational runners, 6 to 9 gels is a realistic range for a full marathon. The exact number depends on your pace and your gel size. This calculator keeps the numbers sensible on purpose - something like 13 gels is not what a normal runner needs or can even stomach.

A gel takes 20-30 minutes to get into your bloodstream. Taking one in the last stretch does nothing for your performance and just adds unnecessary stress on your stomach when you are already pushing hard.

It depends on the temperature. In cold weather, about 400 mL per hour. On a mild day, around 500 mL. When it is warm or hot, closer to 700 mL. The most important thing: drink when you are thirsty, not on a fixed schedule. Drinking too much is actually a bigger problem than drinking a little too little.

For anything under 90 minutes in normal conditions, plain water is fine. On longer runs, especially in the heat, adding sodium through a sports drink or electrolyte tabs helps your body hold onto fluid better. Around 300-500 mg per hour is a good range.

Yes, always. Your gut needs time to get used to taking in gels at race pace. Start with one gel on a long training run and slowly build from there over a few weeks. Never use a new product for the first time on race day.

Plenty of runners do. Chews, dates, small pieces of banana, or a carb drink all work just as well. What matters is getting enough carbs per hour, not which format they come in. Try a few different options in training to see what sits well with you.