Carbs Calculator (Carbohydrates per Day)

Calculate daily carbohydrate needs in grams from body weight, calories, or TDEE based on age, sex, height, weight, and activity level.

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Daily Carbs Formula

The following formulas match the calculator’s logic and show how daily carbohydrate grams are estimated from body data, activity, and a chosen carb percentage.

BMR = 10×W_kg + 6.25×H_cm − 5×a + s
TDEE = BMR × AF
Carbs (g/day) = (TDEE × p) ÷ 4

• W_kg = weight in kilograms (if you enter pounds: W_kg = W_lb × 0.453592).
• H_cm = height in centimeters (if you enter inches: H_cm = H_in × 2.54).
• a = age in years.
• s = +5 for male, −161 for female (Mifflin–St Jeor constant).
• AF = activity factor selected (e.g., 1.2, 1.375, 1.55, 1.725, 1.9).
• p = carbohydrate share of total calories (calculator allows 0.45–0.65; default 0.50). Carbohydrates provide 4 kcal per gram, hence “÷ 4”.

Daily Carbs Definition

This formula is a little dense, so we will break it down a little further. The first step in calculating your daily carb intake is estimating your daily calories needed. This can be done through a number of formulas, but most end up with a very similar result. In this case, we use the Mifflin–St Jeor BMR formula.

Then we take that total calorie estimate (TDEE) and multiply it by your chosen carbohydrate percentage (default 50%; many general guidelines use a range such as 45–65%). Finally, you divide by 4 to convert carbohydrate calories into grams, because each gram of carbohydrate has 4 calories of energy.

Method notes: This tool estimates calories using Mifflin–St Jeor and converts a selected carbohydrate share into grams. For general guidance on macronutrient ranges, check the USDA Dietary Guidelines and the National Academies’ Acceptable Macronutrient Distribution Ranges (AMDR). Last updated: January 1, 2026.