The method
BMR uses Mifflin-St Jeor by default, or Katch-McArdle when you enter body fat. TDEE multiplies BMR by your activity factor. Your target applies your goal adjustment, with a safety floor so the deficit never gets reckless.
Macros: protein is set first (2.0 g/kg when cutting, 1.8 g/kg otherwise — within the 1.6–2.2 g/kg range supported by meta-analysis research), fat at ~25% of calories (never below 0.6 g/kg) and carbohydrates fill the rest to fuel training.
FAQ
How big should my calorie deficit be to get abs?
A deficit of 15–25% below maintenance is a common, sustainable range. It typically produces about 0.5–1% body-weight loss per week while protecting muscle if protein and strength training are in place.
How much protein do I need to keep muscle while cutting?
Research suggests around 1.6–2.2 g per kg of body weight per day, with leaner people in a deficit often benefiting from the higher end.
Should I use Katch-McArdle or Mifflin-St Jeor?
If you know your body fat reasonably well, Katch-McArdle (based on lean mass) can be more accurate. Otherwise Mifflin-St Jeor is a well-validated default. Both are starting points — adjust from real-world weekly averages.