Carbohydrate Calculator

The calculator first estimates how many Calories you burn each day from your age, sex, size and activity, then shows how many grams of carbohydrate fit within common shares of those Calories. The 45% to 65% range is the one recommended for adults by the US Dietary Guidelines.

What are Carbohydrates?

Carbohydrates are one of the three macronutrients, along with protein and fat, and they are the body's main source of quick energy. During digestion most carbohydrates are broken down into glucose, which fuels the brain, muscles and other tissues. Glucose not needed right away is stored as glycogen in the liver and muscles, and any further excess can be converted to fat.

Types of Carbohydrates

Carbohydrates are grouped by the size of their molecules. Sugars are the simplest. Monosaccharides such as glucose, fructose and galactose are single sugar units, and disaccharides such as sucrose (table sugar), lactose (milk sugar) and maltose are two units joined together. Sugars occur naturally in fruit, vegetables and milk, and are added to many processed foods and drinks.

Starches are long chains of glucose units found in grains, potatoes, corn, beans and other plant foods. The body breaks them down into glucose more slowly than sugars, especially when they come packaged with fiber in whole foods. Refined starches, such as white flour and white rice, have had much of that fiber removed and are digested more quickly.

Fiber is the part of plant carbohydrates that the body cannot fully digest. Soluble fiber, found in oats, beans, apples and barley, forms a gel that can lower LDL cholesterol and slow the rise in blood sugar after meals. Insoluble fiber, found in whole wheat, bran, nuts and many vegetables, adds bulk and helps keep bowel movements regular. Adults are advised to eat about 14 grams of fiber per 1,000 Calories, or roughly 25 to 34 grams a day, and most fall well short.

A more useful distinction for everyday eating is between whole and refined sources. Vegetables, fruit, legumes and whole grains provide carbohydrate along with fiber, vitamins, minerals and other beneficial compounds. Sugary drinks, sweets, pastries and many refined snacks supply carbohydrate with little else and tend to raise blood sugar quickly. The Dietary Guidelines recommend keeping added sugars below 10% of daily Calories.

The glycemic index ranks foods by how much they raise blood sugar compared with pure glucose. It can be helpful, particularly for people managing diabetes, but portion size and the rest of the meal matter too, so it works best as a rough guide rather than a strict rule.

How Many Carbs Should I Eat?

For most adults, the Institute of Medicine recommends that 45% to 65% of daily Calories come from carbohydrates, with a minimum of 130 grams a day, the amount the brain needs to run on glucose. On a 2,000-Calorie diet that range works out to 225 to 325 grams. The table in your results shows how the numbers change with your own calorie needs.

For example, a 25-year-old man who is 5 feet 10 inches tall, weighs 160 pounds and exercises lightly needs about 2,360 Calories a day to maintain his weight. At 45% to 65% of Calories, that is about 266 to 384 grams of carbohydrate a day.

Where you fall within the range depends on your activity and goals. Endurance athletes and people who train hard for long periods often benefit from the upper end, or even more, because carbohydrates are the main fuel for sustained exercise and replenish muscle glycogen. Sports nutrition guidelines suggest roughly 3 to 5 grams per kilogram of body weight per day for light training and up to 8 to 12 grams per kilogram for very heavy endurance training.

Lower-carbohydrate diets, with less than about 40% of Calories from carbs, can be effective for weight loss and for improving blood sugar control in some people with type 2 diabetes, largely because they make it easier to eat fewer Calories overall. Over the long term, studies find that weight loss on low-carb and low-fat diets is broadly similar, and the best diet is the one you can keep up. Very low-carbohydrate ketogenic diets, under about 50 grams a day, are restrictive and can cause side effects; people with diabetes or kidney disease, those who take blood-sugar-lowering drugs and pregnant women should speak with a doctor before trying them.

Quality matters at least as much as quantity. Building carbohydrate intake around vegetables, fruit, beans, lentils and whole grains supplies fiber and nutrients and supports steady energy, while relying on sugary drinks and refined snacks does the opposite.

Carbs (g) = daily Calories × carb share ÷ 4

Each gram of carbohydrate supplies about 4 Calories. Daily Calories come from the Mifflin-St Jeor (or Katch-McArdle) BMR multiplied by your activity factor.

Frequently asked questions

Sources

• Dietary Guidelines for Americans
• NIH MedlinePlus – Carbohydrates
• USDA FoodData Central