Daily Macro Calculator

Three steps:

1. BMR (Basal Metabolic Rate) via Mifflin-St Jeor:
   10 * weight(kg) + 6.25 * height(cm) - 5 * age + sex_adjustment
   Sex adjustment is +5 for males, -161 for females. This is your maintenance calories at total rest.
2. TDEE (Total Daily Energy Expenditure) = BMR × activity multiplier (1.2 for sedentary up to 1.9 for athlete).
3. Goal target = TDEE + goal delta (-500 for cut, 0 for maintain, +300 for bulk).

From the calorie target, protein is set first (based on bodyweight and goal), fat is set as a percentage of calories (28%), and carbs fill what is left.

The Harris-Benedict equation (1919, revised 1984) was the standard for decades. The Mifflin-St Jeor equation (1990) was developed specifically because Harris-Benedict over-estimated BMR in modern populations by 5-10%, leading to over-prescribed calories and stalled fat loss.

Mifflin-St Jeor is now the recommended formula in the Academy of Nutrition and Dietetics guidelines. For body-fat-normalized accuracy you would use Katch-McArdle (which requires knowing your body fat percentage). For everyone else, Mifflin-St Jeor is the most accurate readily-available formula.

This is where most calculators get it wrong: people overestimate their activity level. Honest descriptions:

• Sedentary (1.2): Desk job, no formal exercise, less than 5,000 steps/day. This is most knowledge workers who do not go to the gym.
• Light (1.375): Desk job + 1-3 short workouts per week. Or active job + minimal training.
• Moderate (1.55): 3-5 hard workouts per week + general daily activity. This is most regular gym-goers.
• Active (1.725): 6-7 sessions per week, often including hard cardio. Or a physically demanding job + some training.
• Athlete (1.9): 2+ sessions per day, or competitive endurance training, or genuinely heavy manual labor + training.

If your weight is not changing as the math predicts after 4-6 weeks, your real activity level is one notch lower than you picked. This is almost always the issue.

Protein needs are driven by lean body mass and goal, not by total calories. The targets we use:

• Cut (1.0 g/lb): Higher protein during a deficit preserves lean mass. Research supports 0.8-1.2 g/lb for active people losing fat.
• Maintain (0.75 g/lb): The standard "active adult" recommendation.
• Bulk (0.85 g/lb): Slightly higher than maintenance to support muscle protein synthesis during a surplus.

These are higher than the RDA (0.36 g/lb) because the RDA is set to prevent deficiency, not to optimize body composition. If you are sedentary or much older, you can go lower.

After protein is set, fat is fixed at 28% of total calories. The remainder is carbs. Why 28%? It is the middle of the practitioner-recommended 25-35% range, leaves enough carbs for hard training, and is sustainable long-term.

If you prefer a higher-fat or lower-fat approach (keto, low-carb, plant-based), the calculator gives you the calorie and protein targets; you can shift fat and carbs around within the calorie budget. As long as you hit protein and calories, the fat/carb split is largely cosmetic for fat loss or maintenance.

For meal planning, recipes, and specific dietary preferences (vegan, gluten-free, etc.), the Nutrition Copilot builds plans around these targets.

This is a starting point, not a prescription. It will be off if:

• Your body fat percentage is very low (under 10% male / 15% female) or very high (over 35%). Use Katch-McArdle instead.
• You are pregnant or breastfeeding (different needs).
• You have a metabolic condition (thyroid disorders, PCOS, diabetes affecting energy expenditure).
• You are recovering from significant weight loss or have a history of chronic dieting (likely lower TDEE than predicted).

The real test: track for 2-3 weeks and adjust based on what your body actually does, not what the math predicts.