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Carb loading calculator

Short answer

For races longer than 90 minutes, carbohydrate loading means 10–12 g of carbohydrate per kg of body weight a day for the 36–48 hours before. At 70 kg that is 700–840 g a day. During the race itself, 30–60 g an hour suits most longer events, and up to 90 g an hour can help beyond 2.5 hours.

Last reviewed 27 October 20261 published sourcesNot medical advice

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Carb loading calculator

For races longer than 90 minutes, such as a marathon, long triathlon or long ride.

Enter your body weight.

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Carbohydrate a day for loading, by body weight
Body weight	10 g/kg	12 g/kg
50 kg (110 lb)	500 g	600 g
60 kg (132 lb)	600 g	720 g
70 kg (154 lb)	700 g	840 g
80 kg (176 lb)	800 g	960 g
90 kg (198 lb)	900 g	1,080 g
100 kg (220 lb)	1,000 g	1,200 g

For the 36–48 hours before a race longer than 90 minutes.

Where the numbers come from

A review of carbohydrate for training and competition sets carbohydrate loading at 10–12 g/kg a day for 36–48 hours of fuelling before events longer than 90 minutes. For during the race, it puts 30–60 g an hour as a target for longer sports, and up to 90 g an hour for events beyond 2.5 hours, using blends of different carbohydrates (Burke et al., 2011).

Work out your day-to-day calories with the TDEE calculator and your macro split with the macro calculator. Plan your race pace with the race time predictor.

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Common questions

How many carbs should I eat before a marathon?

10–12 g per kg of body weight a day for the 36–48 hours before. For a 70 kg runner that is about 700–840 g a day.

Do I need to carb load for a 10k or half marathon?

Carbohydrate loading is aimed at events longer than about 90 minutes. For shorter races, normal eating with a carbohydrate-rich meal before is usually enough.

Why do I weigh more after carb loading?

Stored carbohydrate (glycogen) holds water with it, so the scale often goes up a little. That stored fuel is the point of loading.

Sources

Figures on this page were checked against these publications on 27 October 2026.

Burke LM, Hawley JA, Wong SHS, Jeukendrup AE. Carbohydrates for training and competition. Journal of Sports Sciences. 2011;29(Suppl 1):S17–S27. doi.org/10.1080/02640414.2011.585473

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