Carbs Calculator

Using the carbs calculator step by step

1. Enter your age in years, your sex, your height (feet and inches for US units, centimetres or metres for metric) and your weight in pounds or kilograms.
2. Pick the activity level that matches a typical week, from sedentary to extreme.
3. Set the carbs percentage, the share of your daily calories you want from carbohydrate. It starts at 50% and cannot be lower than 10%.
4. Press Calculate.

You get five lines: the carbohydrate calories and grams that keep your weight stable, two lower targets for losing weight, and two higher targets for gaining it. With US units the amount is shown in ounces; with metric units it is in grams.

How the numbers are calculated

First the calculator estimates your resting energy use with the Mifflin-St Jeor equation, then scales it by your activity level to get your daily calorie need (often called TDEE).

BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age + 5 (men)

BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age − 161 (women)

carbohydrate calories = daily calories × carbs %Carbohydrate supplies about 4 kilocalories per gram, so grams = calories ÷ 4.

The weight-change lines adjust the daily calories before applying the percentage: 500 fewer calories a day for the first loss target, 1,000 fewer for the second, and 500 or 1,000 more for the gain targets. About 3,500 kcal corresponds to one pound of body weight, so a 500 kcal daily gap is roughly a pound a week. This is a rule of thumb, and real results vary from person to person.

Worked examples

US units. A 35-year-old woman is 5 ft 6 in tall (167.6 cm), weighs 150 lb (68.0 kg), exercises moderately and wants 45% of her calories from carbohydrate.

• BMR = 10 × 68.04 + 6.25 × 167.64 − 5 × 35 − 161 = 1,392 kcal.
• Daily calories = 1,392 × 1.55 = 2,158 kcal.
• Carbohydrate calories = 2,158 × 0.45 = 971 kcal, which is 971 ÷ 4 = 243 g, or 8.56 ounces.
• Losing a pound a week means 2,158 − 500 = 1,658 kcal, of which 45% is 746 kcal, or about 187 g of carbohydrate.

Metric units. A 28-year-old man is 180 cm tall, weighs 78 kg, trains hard 6 to 7 days a week and chooses 55%. His BMR is 1,770 kcal, his daily calories are 1,770 × 1.725 = 3,053 kcal, and carbohydrate calories are 3,053 × 0.55 = 1,679 kcal, or 420 g a day. For a deficit of about half a kilogram a week the calculator gives 1,404 kcal of carbohydrate, which is 351 g.

How many carbs do you need?

The US Institute of Medicine sets a recommended dietary allowance of 130 g of carbohydrate per day for adults and children, the amount needed to supply the brain with glucose. It also gives an acceptable range of 45% to 65% of calories, which is the guidance echoed in the Dietary Guidelines for Americans. Most people eat well above the minimum, and where in the range to sit depends on appetite, health conditions, food preferences and training load.

The quality of the carbohydrate matters as much as the amount. Aim for most of it to come from vegetables, fruit, legumes, whole grains and dairy, keep added sugars under about 10% of calories, and look for roughly 14 g of fibre per 1,000 kcal.

Results are estimates for healthy adults, not medical advice. People with diabetes, kidney disease or other conditions, and anyone who is pregnant or under 18, should get personal advice from a doctor or registered dietitian. See our disclaimer.

Carbohydrate intake for athletes

Athletes often plan carbohydrate by body weight instead of by percentage, because the need rises with training volume. Sports nutrition guidelines (for example the joint position of the American College of Sports Medicine and the Academy of Nutrition and Dietetics) suggest these daily ranges:

A 70 kg runner training one to three hours a day would therefore look at 6 × 70 = 420 g up to 10 × 70 = 700 g. During sessions longer than an hour, 30 to 60 g of carbohydrate per hour is commonly advised to sustain performance. Eating more than your training needs does not add benefit, and an easy week calls for a lower figure.

Lower-carbohydrate approaches

Definitions differ between studies, but a low-carbohydrate diet is often described as under 130 g a day or under about a quarter of calories, and a very low-carbohydrate (ketogenic) diet as roughly 20 to 50 g a day or under 10% of calories. To explore these with the calculator, lower the carbs percentage; the minimum allowed is 10%.

Cutting carbohydrate does not change the energy balance by itself. Weight change still depends on total calories, which is why the calculator derives carbs from a calorie target. For the other macronutrients, the macronutrient calculator, protein calculator and fat intake calculator use the same approach, and the TDEE calculator shows the daily calorie estimate on its own.

Common carbohydrate foods

Slower carbohydrates come with fibre and protein and raise blood sugar gradually (whole grains, legumes, most fruit and vegetables). Faster ones are quickly digested (white bread, sugary drinks and sweets). Approximate carbohydrate content per 100 g, based on USDA food composition data: