Carb Loading Calculator — Body Weight → Daily Grams
Enter your body weight and race distance to see your daily carbohydrate target for the carb load period — how many grams per day, what that means for breakfast, lunch, and dinner, and how many days before the race to start.
Enter your body weight to see your carb load plan.
How the carb loading calculator works
Carb loading maximizes muscle glycogen stores before a long race. The evidence-based target from the sports nutrition literature is 8 to 12 grams of carbohydrate per kilogram of body weight per day, spread across meals and snacks, for 24 to 72 hours depending on race distance.
For shorter races (10 km, half marathon), a single day at 8 g/kg is enough. For a full marathon, 48 hours at 10 g/kg works for most athletes. For a full Ironman or ultra, 72 hours at 10 to 12 g/kg is the standard protocol, with the last 24 hours emphasizing low-fiber, high-glycemic foods to minimize gut issues on race morning.
A 70 kg athlete targeting 10 g/kg/day needs 700 g of carbohydrate per day. That's a lot — roughly 2,800 kcal from carbs alone, which means three main meals plus three or four snacks, all carb-heavy. Rice, pasta, potatoes, bread, fruit, and sports drinks do most of the work.
The week before the race, keep fat and fiber moderate and protein normal. You are adding carbs, not substituting them for other macros. Weight gain of 1 to 2 kg during the load is normal — it's water bound to stored glycogen, and it will disappear by kilometer 20 of the marathon.
Daily carbs (g) = body weight (kg) × target (g/kg) · Typical target: 8 g/kg (short), 10 g/kg (marathon/70.3), 10–12 g/kg (full Ironman)
Frequently asked questions
How many days before the race should I start?
For a 10 km or half marathon, 24 hours is enough. For a full marathon or a 70.3, start 48 hours before the race. For a full Ironman or ultra-marathon, 72 hours is the standard — although many experienced athletes do 48 hours at the higher range (12 g/kg) and get equivalent results with less digestive load.
Will carb loading make me feel heavy?
Yes, slightly. Every gram of glycogen stored binds about 3 grams of water, so a successful carb load shows up as 1 to 2 kg of temporary weight gain. This is the point — it's fuel for the race. The feeling of heaviness goes away within 30 to 60 minutes of starting the race as you begin burning glycogen.
What if I can't eat 700 grams of carbs in a day?
You probably can — you just need liquid carbs to bridge the gap. A bottle of sports drink (40 to 60 g) between meals, a carb gel as an afternoon snack, white rice instead of brown, and fruit juice at breakfast together close the last 150 to 200 g easily. If solid food volume is the bottleneck, shift toward low-residue liquids in the final 24 hours.
Is carb loading necessary for a 10 km?
Not really. A 10 km lasts 30 to 60 minutes and muscle glycogen is rarely the limiter. A normal carb-forward dinner the night before is sufficient. Carb loading starts mattering at efforts longer than about 90 minutes where glycogen depletion becomes a real risk.
Cora plans your race-week nutrition
Tell Cora your race and body weight and she generates your carb-load schedule day by day, with meal suggestions built from your food preferences. She adjusts for race distance, for heat, and for any GI sensitivities you have told her about — so you arrive on race morning topped up and not bloated.