Carb loading calculator
How many grams of carbs to eat each day before your race, based on your weight, race and finish time. The same rules the Mavr app uses.
Want your carb load set up for your next race? See Mavr on the App Store
General guidance for healthy adults, not medical advice. Talk to a doctor or registered dietitian if you have a health condition, take medicines or have special dietary needs.
How this carb loading calculator works
Carb loading means eating more carbohydrate for 2 to 3 days before a long race so your muscles start full of glycogen.
Races of 90 minutes or more, or 15 km or more, get a carb load. A half marathon under 3 hours loads for 2 days, at 7 then 8 g of carbs per kg of body weight. A marathon, ultra or triathlon, or any race over 3 hours, loads for 3 days at 8, 9, then 10 g per kg.
Sports nutrition guidelines from the ACSM and IOC put a full carb load at 10 to 12 g per kg for 36 to 48 hours. Mavr builds up to 10 g per kg over three days, because a gradual rise is easier on the stomach than jumping straight to the top.
- 1Enter your body weight in kg or lb.
- 2Pick your race and your expected finish time.
- 3Turn on Sensitive stomach if big meals upset you before races.
- 4See the grams for each day, a fiber limit, and an example day of food.
How many carbs to carb load, by body weight
Grams on the biggest day, the day before the race, and the total for a 3-day marathon load.
| Body weight | Half marathon, day before | Marathon, day before | Marathon, 3 days total |
|---|---|---|---|
| 50 kg (110 lb) | 400 g | 500 g | 1,350 g |
| 60 kg (132 lb) | 480 g | 600 g | 1,620 g |
| 70 kg (154 lb) | 560 g | 700 g | 1,890 g |
| 80 kg (176 lb) | 640 g | 800 g | 2,160 g |
| 90 kg (198 lb) | 720 g | 900 g | 2,430 g |
When to start carb loading
Start 3 days before a marathon or longer race, and 2 days before a half marathon. Keep training light on those days so the extra carbs are stored, not burned.
You do not need the old week-long version with a low-carb "depletion" phase first. A few days of high carbs fills your stores just as well.
- Marathon, ultra, triathlon3 days before, at 8, 9, then 10 g per kg. Also any race over 3 hours.
- Half marathon2 days before, at 7 then 8 g per kg.
- Under 90 minutesNo load. Eat normal carb-rich meals the day before.
Best carb loading foods
Pick carbs that are easy to eat in large amounts and low in fiber and fat.
- Eat moreWhite rice, pasta, bagels, white bread, peeled potatoes, low-fiber cereal, bananas, juice, sports drinks, pretzels, honey, jam
- Eat lessWholegrain bread and pasta, beans and lentils, big salads, nuts and seeds, fried and creamy foods
- Drinks helpJuice and sports drinks add carbs without making you feel full
Common carb loading mistakes
- One huge pasta dinnerOne meal cannot fill your stores. Spread carbs across every meal and snack.
- Too much fiberWholegrains and vegetables fill you up and can upset your stomach on race day.
- Adding fat with the carbsCreamy sauces and butter add calories, not glycogen. Cut fat to make room.
- New foodsRace week is not the time to try something new. Use foods you have eaten before long runs.
- Worrying about the scaleGaining 1 to 2 kg is normal. Glycogen is stored with water, and that water helps you on the course.
Carb loading FAQ
Quick answers on how much to eat, when to start, and what to expect on the scale.
Do I need to carb load for a 10K?
No. For races under 90 minutes, normal carb-rich meals the day before are enough. Your stores are already full if you have been eating well.
How many grams of carbs should I eat per day when carb loading?
7 to 10 g per kg of body weight, depending on the race. A half marathon under 3 hours loads at 7 then 8 g per kg. A marathon or longer loads at 8, 9, then 10 g per kg, so a 70 kg runner eats 560 g, 630 g, then 700 g.
Is one pasta dinner the night before enough?
No. One meal cannot fill your stores. Spread carbs across every meal and snack for 2 to 3 days, and make lunch the biggest carb meal the day before so it is digested by race morning.
Will carb loading make me gain weight?
Yes, 1 to 2 kg is normal. Each gram of glycogen is stored with about 3 g of water. It is fuel and fluid you use during the race, not fat.
Should I carb load for a half marathon?
Yes, a short load. The calculator loads for 2 days at 7 then 8 g per kg. If you expect to take more than 3 hours, it loads for 3 days like a marathon.
What should I eat on race morning?
1 to 4 g of carbs per kg, 1 to 4 hours before the start. The more time you have, the more you can eat. Keep it low in fiber and fat: a bagel with jam, white toast with honey, a banana, or a sports drink.