Marathon Fuelling Calculator
Work out exactly how many carbs, fluids, sodium, and gels you need on race day, based on your goal finish time and body weight.
Build Your Fuelling Plan
Enter your goal finish time, body weight, and target intake rates to get a full breakdown of the carbs, fluid, sodium, and gels you’ll need over the race.
Fuelling Calculator
Enter your race details to build a plan
Your Fuelling Plan
Based on your goal finish time and targets
Carb Intake by Finish Time
Approximate total carbohydrate needed over a marathon at a 60g/hr intake rate, for quick lookup against your own goal time.
| Goal Finish Time | Total Carbs (60g/hr) | Approx. Gels Needed* |
|---|---|---|
| 3:00 | 180g | ~7 gels |
| 3:30 | 210g | ~8 gels |
| 4:00 | 240g | ~10 gels |
| 4:30 | 270g | ~11 gels |
| 5:00 | 300g | ~12 gels |
| 5:30 | 330g | ~13 gels |
| 6:00 | 360g | ~14 gels |
Marathon Fuelling FAQ
Everything you need to know about planning your carbohydrate, fluid, and sodium intake on race day.
Most runners perform best around 30 to 60 grams of carbohydrate per hour. Well-trained runners with a gut trained for higher intake can push toward 90 grams per hour or more, often using gels or drinks that combine glucose and fructose, which the body can absorb faster than a single sugar source alone.
A common starting point is 400 to 800 millilitres per hour, adjusted for body size, pace, and weather. Hot or humid races generally call for more fluid, while cooler conditions may need less. Practising your own sweat rate in training is more reliable than any single generic number.
If a gel provides about 25 grams of carbohydrate, a runner targeting 60 grams per hour over a 4-hour marathon needs roughly 9 to 10 gels, or an equivalent mix of gels, chews, and sports drink. Use the calculator above with your own gel’s carb content for an exact figure.
Many coaches suggest taking your first carbohydrate intake within the first 20 to 30 minutes rather than waiting until you feel low on energy, then continuing at regular intervals for the rest of the race. Starting early helps maintain steady blood glucose instead of trying to recover from a deficit later on.