01What this calculator tells you
This calculator estimates how many grams of carbohydrate to eat per day. You can enter your daily calorie target directly, or let the calculator estimate it from your age, sex, height, weight and activity using the Mifflin-St Jeor equation. Then pick a carb goal — low, moderate or high — and it converts calories into grams and shows all three ratios side by side.
Carbohydrate is your body’s main energy source, and how much you need depends on your total calories and how active you are. The federal Dietary Guidelines for Americans recommend most calories come from nutrient-dense carbs like whole grains, fruit and vegetables. To size up your protein and overall energy too, see our BMR calculator.
02How much of your diet should be carbs?
The NIH Office of Dietary Supplements and the Institute of Medicine set the Acceptable Macronutrient Distribution Range for carbohydrate at 45-65% of calories. Where you sit in that band depends on your goals and activity.
Not all carbohydrate is equal. Complex carbs from whole grains, beans and vegetables digest slowly and come packed with fibre; simple sugars spike blood glucose and add little else. The Dietary Guidelines suggest keeping added sugars under 10% of daily calories, and the NHS recommends basing meals on higher-fibre starchy foods.
- Aim for roughly 14 g of fibre per 1,000 calories.
- Choose whole grains, fruit, vegetables and legumes first.
- Treat sugary drinks and sweets as occasional extras.
- People with diabetes should count carbs with their care team — see the CDC.
03Related calculators
Working through a related project? Try our Starbucks Calorie Calculator, Protein Intake Calculator, and BMI Calculator.
01The carb formula
Carbohydrate supplies about 4 calories per gram, so converting a calorie target into grams is straightforward: take the share of calories you want from carbs and divide by 4. The only extra step is knowing your total daily calories, which you can enter directly or estimate from your body and activity.
Where:
- TDEE= total daily energy expenditure — the calories you burn in a day.
- BMR= basal metabolic rate: 10×kg + 6.25×cm − 5×age + 5 (male) or −161 (female).
- carb%= the fraction of calories you want from carbohydrate (0.45-0.65 typical).
02Worked example
Take a moderately active person whose daily energy is 2,000 calories, aiming for a moderate 50% carb split:
So this person needs about 250 g of carbohydrate a day. At a low 20% split it would be 100 g, and at a high 60% split about 300 g — which is why the calculator shows all three. To balance it with fluids, our water intake calculator estimates your daily hydration target.