IIFYM / Macros Calculator

Macronutrients (macros) are the three main nutrients that provide energy: protein, fat, and carbohydrates. Knowing your daily macro targets helps you reach your fitness goal — whether it's losing weight, maintaining, or building muscle.

First, the calculator estimates your Basal Metabolic Rate (BMR) using either the Mifflin-St Jeor or Harris-Benedict formula, then multiplies it by an activity factor — a method endorsed by the American Council on Exercise (ACE) — to get your Total Daily Energy Expenditure (TDEE). The calorie target is then adjusted by your goal (−500 kcal for loss, +300 kcal for gain). Macros are split as a percentage of total calories.

Weight loss subtracts 500 kcal from TDEE — a moderate deficit that targets ~0.5 kg/week of fat loss. Maintenance keeps calories at TDEE. Weight gain adds 300 kcal — a lean bulk that minimises fat gain.