About the Carb Loading Calculator
Carbohydrate loading tops up the glycogen stored in your muscles and liver before a long endurance event, so you can hold race pace for longer before fatigue sets in. This carb loading calculator converts the sports-nutrition guideline of 10–12 grams of carbohydrate per kilogram of body weight per day, for the 36–48 hours before a race, into a daily gram target, a per-meal amount and a day-by-day plan.
It is meant for marathoners, half-Ironman and Ironman triathletes, long-distance cyclists, cross-country skiers and anyone racing for more than about 90 minutes. For shorter events, normal training-day carbohydrate is usually enough.
Carb loading works best alongside a training taper, so your muscles are not burning the glycogen you are storing. Expect to gain a little weight from the water stored with glycogen — that is normal. Practise your loading foods before a key race, and favour lower-fibre options so your gut is comfortable on race morning.
With the default inputs, the carbohydrate per day is 680 g/day. Change any value above to recalculate instantly.
How to use the carb loading calculator
- 1Enter your body weight in pounds or kilograms.
- 2Choose a carb target — 10 g/kg suits most runners; try 8 g/kg if you are new to loading.
- 3Pick how many days you will load (36–48 hours is standard).
- 4Set how many meals and snacks you will eat each day.
- 5Follow the day-by-day table, choosing low-fibre, low-fat carbohydrate foods.
Formula and method
Sports-nutrition guidelines from the American College of Sports Medicine, Academy of Nutrition and Dietetics and Dietitians of Canada recommend 10–12 g of carbohydrate per kilogram of body weight per day for the 36–48 hours before events lasting longer than about 90 minutes. The calculator multiplies your weight in kilograms by the target you choose and spreads it across your meals and snacks.
Carbohydrate provides about 4 kcal per gram, which gives the calorie figure. For comparison, the chart shows a typical moderate training day of 5 g/kg. The pre-race meal range uses the guideline of 1–4 g/kg eaten 1–4 hours before the start. Weight in pounds is converted at 1 lb = 0.4536 kg.
- kg
- Body weight in kilograms
- target
- Carbohydrate grams per kg per day (8, 10 or 12)
- meals
- Number of meals and snacks per day
Worked examples
150 lb marathoner, 10 g/kg for 2 days
150 lb is 68.0 kg, so 10 g/kg gives about 680 g of carbohydrate a day — roughly 113 g at each of six meals and snacks, or 2,722 kcal from carbs alone. Over two days that is about 1,361 g.
60 kg runner, maximum load for 1 day
At 12 g/kg a 60 kg athlete needs 720 g of carbohydrate in the final day, or 144 g at each of five meals. That is 2,880 kcal from carbohydrate.
190 lb cyclist, lighter 3-day load
190 lb is 86.2 kg; at 8 g/kg that is about 689 g a day, 115 g per meal across six eating occasions, and roughly 2,068 g over three days.
Frequently asked questions
How many carbs should I eat before a marathon?+
Sports-nutrition guidelines recommend 10–12 g of carbohydrate per kg of body weight per day for the 36–48 hours before the race — about 680–820 g a day for a 68 kg (150 lb) runner.
Do I need to carb load for a half marathon or 10K?+
Carb loading is mainly useful for events longer than about 90 minutes. For events under 90 minutes, such as a 10K or a fast half marathon, the ACSM position statement suggests 7–12 g/kg over the preceding 24 hours — the same as a normal high-carbohydrate training day — rather than a full 36–48-hour load.
What are the best foods for carb loading?+
Choose easy-to-digest, lower-fibre carbohydrates: white rice, pasta, bagels, white bread, potatoes without skin, pancakes, bananas, juice, sports drinks and sweets. Keep fat and fibre modest so the volume is manageable.
Will carb loading make me gain weight?+
Yes, temporarily. Each gram of stored glycogen is stored with water, so a gain of around 1–2 kg (2–4 lb) is common and expected; it is fuel, not fat.
Should I eat a big pasta dinner the night before?+
A single huge meal is less effective than spreading carbohydrate over the final 36–48 hours, and it can upset your stomach on race morning. Eat moderate, carb-rich meals and snacks throughout the days before.
This tool gives general estimates and is not medical advice. Talk to a doctor or qualified professional about your health, diet or training.