Carbohydrate Calculator

Work out how many grams of carbohydrate to eat per day, based on your calorie needs and the 45–65% Acceptable Macronutrient Distribution Range.

Sex
Height cm
ft in
Activity level
  • Sedentary — little or no exercise
  • Light — exercise 1–3 days/week
  • Moderate — exercise 3–5 days/week
  • Active — exercise 6–7 days/week
  • Very active — hard exercise or physical job
Goal
  • Maintain weight
  • Lose weight (−0.5 kg/week)
  • Gain weight (+0.5 kg/week)
Calorie formula
  • Mifflin-St Jeor (recommended)
  • Harris-Benedict
  • Katch-McArdle (uses body fat)
Recommended carbs —g/day
Enter your details
Daily calorie target—
Recommended range—
Share of total calories—

From your calorie target and the IOM Acceptable Macronutrient Distribution Range for carbohydrate.

Carbohydrate is your body’s main source of everyday energy, especially for your brain and for higher-intensity exercise. How much you need scales with your total calories — so this calculator estimates your energy needs first, then converts them into a daily carbohydrate range in grams.

How your carb target is calculated

  1. Calories. Your daily energy needs are estimated from the Mifflin-St Jeor equation, your activity level, and your goal.

  2. The range. The Institute of Medicine’s Acceptable Macronutrient Distribution Range (AMDR) for carbohydrate is 45–65% of total calories. Because carbohydrate provides 4 kcal per gram, the grams are:

    carbs (g) = calories × 0.45…0.65 ÷ 4

Worked example

On a 2,000-calorie day:

  • Low end: 2,000 × 0.45 ÷ 4 = 225 g
  • High end: 2,000 × 0.65 ÷ 4 = 325 g

The minimum requirement is separate: the RDA of 130 g/day covers the glucose your brain needs, regardless of calorie intake.

Choosing where to sit in the range

Lean toward the higher end if you train hard or do endurance sport, since carbohydrate refills muscle glycogen. Lean toward the lower end if you’re mostly sedentary or deliberately reducing carbs. Wherever you land, prioritise quality — whole grains, fruit, vegetables, and legumes bring fiber and nutrients that refined carbohydrates don’t.

Frequently asked questions

How many grams of carbs should I eat per day?

The Institute of Medicine recommends 45–65% of your calories come from carbohydrate. On a 2,000-calorie day that's about 225–325 g. This calculator finds your calorie needs first, then applies that range to give your grams.

Why does a carb calculator need my height and age?

Because carb targets are based on your total calories, and calories depend on your size, age, sex, and activity. The tool estimates your daily energy needs with the Mifflin-St Jeor equation, then takes 45–65% of that as carbohydrate.

What's the minimum carbohydrate I need?

The RDA is 130 g/day, the amount needed to supply the brain with glucose. Very-low-carb (keto) diets go below this and rely on ketones instead; they can work for some people but aren't required for most.

Should I focus on carb quality too?

Yes. The gram target is only half the picture — most carbs should come from whole grains, fruit, vegetables, and legumes rather than refined sugars and starches, which affects fiber, satiety, and blood-sugar response.

References