How this calculator works
The calculator estimates your basal metabolic rate using Mifflin-St Jeor, multiplies it by your activity level to get TDEE, then applies your goal multiplier. Macros are allocated in a fixed priority: protein first (based on body weight), fat second (as a percentage of target calories), and carbohydrates fill the remainder.
This protein-first approach ensures you hit the minimum threshold for muscle protein synthesis regardless of whether you are cutting, maintaining, or bulking. The fat floor prevents hormonal disruption (going below 20 % of calories from fat is not recommended for most people). Carbohydrates flex up or down to balance the energy budget.
Why protein first
Three reasons protein gets priority in any macro split:
- Satiety. Protein is the most filling macronutrient per calorie. Higher protein intakes reduce hunger and spontaneous snacking, which makes a calorie deficit easier to sustain.
- Thermic effect of food (TEF). Your body uses roughly 20-30 % of protein calories just to digest and process them, compared to 5-10 % for carbs and 0-3 % for fat. Higher protein means slightly higher total energy expenditure.
- Lean mass preservation. During a calorie deficit, adequate protein (1.6-2.2 g/kg) minimises muscle loss. During a surplus, it supports muscle gain alongside resistance training.
FAQ
Do I need to hit my macros exactly every day?
No. Weekly averages matter more than daily precision. If you are within 10 g of each target on most days, you are doing well. Obsessing over single-gram accuracy creates unnecessary stress and is not supported by the research.
What if my carbs come out very low on a cut?
If your carb target drops below roughly 100 g, consider reducing your fat percentage to free up more calories for carbohydrates. Extremely low carbs can impair training performance and recovery, especially for high-intensity exercise. Alternatively, slightly reduce protein toward 1.6 g/kg — the difference in muscle retention between 1.6 and 2.2 g/kg is small for most people.