Race Fueling Calculator
Get a personalized race nutrition plan: how many gels, when to take them, hydration targets, and pre-race meal timing.
Your Fueling Plan
Carbs/Hour
75g
Gels Needed
12
Hydration/Hour
400ml
Sodium/Hour
400mg
Gel Schedule
Pre-Race Meal
When: 2 to 3 hours before start
Target: 105g carbs
Example: 105g carbs = 3 slices of toast with jam, or 4 bananas, or a bowl of oatmeal with honey
Stick to foods you have tested in training. Avoid high fiber and high fat.
Caffeine Strategy (optional)
Recommended dose: 280mg
Take 280mg caffeine 45 to 60 minutes before the race, or split into the second half via caffeinated gels
Common Fueling Mistakes
Trying something new on race day
Never eat or drink anything in a race that you have not tested in training. Your gut needs practice digesting fuel while running. Test your gel brand, timing, and hydration strategy on long runs first.
Waiting too long for the first gel
Many runners wait until they feel tired to start fueling, but by then your glycogen stores are already depleted. Take your first gel at 30 to 45 minutes and maintain a consistent schedule.
Taking gels without water
Most gels need water to digest properly. Taking a gel without water can cause stomach cramps and nausea. Time your gels with aid stations or carry a small bottle.
Overdrinking water
Hyponatremia (dangerously low sodium) from overdrinking is more dangerous than mild dehydration. Drink to thirst, not on a rigid schedule. Include electrolytes on runs over 90 minutes.
Eating a big meal too close to race start
Your pre-race meal should be 2 to 3 hours before the start to allow digestion. Eating too close to start time diverts blood to your stomach and causes cramps.
Ignoring sodium and electrolytes
You lose 300 to 1000mg of sodium per hour through sweat. Plain water alone does not replace this. Use electrolyte drinks or salt tablets for races over 90 minutes, especially in hot weather.
Frequently Asked Questions
Frequently Asked Questions
How many gels do I need for a marathon?
Most marathon runners need 5 to 8 gels depending on the brand (carbs per gel vary from 20 to 30g) and their target carb intake (60 to 90g per hour). For a 4 hour marathon at 60g/hr, that is 240g total, or about 10 to 11 standard gels. Start fueling at 30 minutes and take a gel every 30 to 45 minutes.
Do I need to fuel during a 5K or 10K?
No. For races under 60 minutes, your body has enough stored glycogen to fuel the effort. Just eat a normal pre-race meal 2 to 3 hours before. Fueling during the race can actually cause stomach issues without providing any performance benefit at these distances.
When should I take my first gel during a race?
Take your first gel at 30 to 45 minutes into the race. This is before you feel tired, which is the point. You want to maintain glycogen levels, not try to recover them after depletion. Think of it as topping off the tank, not refilling an empty one.
How much water should I drink during a marathon?
Drink 400 to 800ml per hour, adjusting for heat and your personal sweat rate. A good rule is to drink when thirsty and take a few sips at every aid station. Do not force large volumes. Overdrinking can cause hyponatremia, which is more dangerous than mild dehydration.
What should I eat the morning before a race?
Eat 1 to 2 grams of carbohydrates per kilogram of body weight, 2 to 3 hours before the start. Good options include toast with jam and banana, oatmeal with honey, a bagel with peanut butter, or a bowl of cereal. Avoid high-fiber, high-fat, and spicy foods. Stick to foods you have eaten before training runs.
Does caffeine help running performance?
Yes. Research consistently shows caffeine improves endurance performance by 2 to 4%. The optimal dose is 3 to 6mg per kilogram of body weight, taken 45 to 60 minutes before the race. For a 70kg runner, that is 210 to 420mg, equivalent to 2 to 4 cups of coffee. Some runners prefer taking caffeinated gels in the second half of longer races.
What is the difference between 30g and 90g of carbs per hour?
30g per hour is sufficient for runs of 1 to 2.5 hours. For longer efforts (2.5 hours and beyond), research shows trained guts can absorb 60 to 90g per hour using a mix of glucose and fructose. Higher intake requires practice and building up gradually over several weeks of training.
Can I use real food instead of gels?
Yes. Many ultrarunners use real food like dates, rice balls, pretzels, baby food pouches, or PB&J sandwiches. The key is getting enough carbs per hour from whatever source works for your stomach. Gels are simply the most convenient and portable option for shorter races.
