Build a race fuel plan you can actually practise
Estimate carbohydrate needs, gel servings, drink carbs and approximate fuel checkpoints for a half marathon, marathon, 50K or custom race. Use the result as a training plan to test, not a guarantee that your stomach will tolerate a certain intake.
Plan your race fuel
Choose a carbohydrate target you have practised. More is not automatically better if your gut is not ready for it.
Race and finish time
Used for total fuel and approximate checkpoint locations.
Carbohydrate target
Choose what you want to test, not the biggest number available.
Choose your gel or fuel serving
Use a preset or enter the carbohydrate shown on your own fuel label.
Not sure which gel to use? Compare the Best Energy Gels for Running for carb content, sodium, caffeine, texture and current picks.
Add carbohydrate from drinks
Optional. Enter a fluid rate you already use or plan to test. This is not a universal drinking recommendation.
Your race fuel plan
Approximate fuel checkpoints
Distance assumes an even average pace. Use the time column if hills, crowds or pacing make distance less predictable.
| Race time | Approx. distance | Fuel |
|---|
DIY sugar + electrolyte training bottle
Build a low-cost table-sugar training drink. If you enter your own sodium concentration, the calculator also estimates how much table salt supplies roughly that sodium amount.
Estimate your sweat rate from a training run
This estimates fluid loss in the conditions of one training run. It is not automatically the amount you should force yourself to drink every hour.
Why grams per hour?
During-event carbohydrate guidance is normally expressed as grams per hour. A common framework is about 30–60 g/hour for 1–2.5 hours and up to 90 g/hour for longer endurance exercise.
Why not force 90 g/hour?
Higher intakes are being studied and used by some trained endurance athletes, but gut tolerance, intensity and what you have practised still matter. The calculator keeps the target editable.
Why hydration stays separate
Sweat rate and sweat sodium vary widely. This tool can describe a planned drink and estimate sweat rate without pretending one fluid or sodium number fits everyone.
Need fuel for the plan?
Compare carbohydrate per serving, texture, caffeine options and cost in the RunningGearLab energy gel guide.
Compare Energy Gels for RunningMarathon fueling calculator FAQ
How many carbs per hour should I take during a marathon?
For endurance exercise lasting more than about 2.5 hours, up to 90 g of carbohydrate per hour is a commonly used evidence-based target range, with 60–90 g/hour widely used for longer events. That does not mean every runner should jump straight to 90 g/hour. Practise the amount you plan to race with.
How many gels do I need for a marathon?
It depends on race duration, carbohydrate target, carbohydrate per gel and whether some carbohydrate comes from sports drink. The calculator subtracts drink carbohydrate before estimating gel servings.
Can table sugar work in a homemade running drink?
Table sugar is sucrose, which supplies glucose and fructose after digestion. Research supports sucrose as a usable carbohydrate source during endurance exercise. Test homemade drinks gradually, especially as concentration rises.
Does the sweat-rate result tell me exactly how much to drink?
No. Sweat rate changes with temperature, pace, clothing and acclimation. Drinking beyond fluid losses can be dangerous, so use the result as one piece of information rather than a command to drink that exact amount every hour.
Should I copy another runner’s sodium plan?
No. Sweat sodium concentration varies substantially between runners. Use your own testing and experience rather than copying a fixed sodium number from someone else.
- During-event carbohydrate guidance commonly uses 30–60 g/hour for roughly 1–2.5 hours and up to 90 g/hour for longer endurance events.
- Precision PF 30 provides 30 g carbohydrate; PF 90 contains 90 g total; Precision Carb & Electrolyte Mix provides 60 g carbohydrate and 1,000 mg sodium per litre.
- Maurten Gel 100 provides 25 g carbohydrate and Gel 160 provides 40 g.
- Sweat rate can be estimated from body-mass change plus fluid intake, minus urine loss, divided by exercise duration.
- Higher carbohydrate targets and homemade fuel should be practised in training before race day.