Macro Nutrient Calculator
Calculate your daily calorie target and macro split (protein, carbs, fat) based on your body stats, activity level, and goal. Uses the Mifflin-St Jeor BMR formula.
How are macros calculated?
The calculation starts with your Basal Metabolic Rate (BMR) — the number of calories your body burns at complete rest. This calculator uses the Mifflin-St Jeor equation, which is considered the most accurate of the commonly used BMR formulas for most adults:
- Men: BMR = (10 × kg) + (6.25 × cm) − (5 × age) + 5
- Women: BMR = (10 × kg) + (6.25 × cm) − (5 × age) − 161
BMR is then multiplied by your activity level (the Harris-Benedict activity multiplier) to get your Total Daily Energy Expenditure (TDEE) — the total calories you burn in a day. A calorie surplus or deficit is applied based on your goal, and the result is split into macros using percentage ratios appropriate for each goal.
What are macronutrients?
Macronutrients are the three main nutrients that provide energy: protein (4 kcal/g), carbohydrates (4 kcal/g), and fat (9 kcal/g). Each plays a distinct role:
- Protein — builds and repairs muscle tissue, supports immune function, and provides satiety. Generally 0.7–1.2 g per pound of body weight for active individuals.
- Carbohydrates — the primary fuel for the brain and high-intensity exercise. Not inherently fattening — excess calories from any source cause fat gain.
- Fat — essential for hormone production, vitamin absorption (A, D, E, K), and cell membrane integrity. Should not drop below 20% of total calories.
Frequently asked questions
How accurate is my TDEE estimate?
TDEE estimates from formulas are typically accurate within ±10–15% for most people. Activity multipliers are rough categories — someone who "exercises 3 days a week" but has a very physical job will have a higher true TDEE than the formula suggests. Tracking calories for 2–3 weeks and comparing with actual weight change is the most reliable calibration method.
Do I need to track every macro?
For most people, hitting a daily protein target and staying within total calories is sufficient. Precise carb-to-fat ratios matter less than protein intake and overall calorie balance. Macro tracking is most useful during cutting phases where small margins matter.
How large a deficit should I use to lose fat?
A 500 kcal daily deficit targets approximately 0.5 kg (1 lb) of fat loss per week. Larger deficits risk muscle loss and hormonal disruption. A 300–500 kcal deficit is generally sustainable for most people without significant muscle loss when protein intake is adequate.
