How this calculator works

1. Resting energy (BMR) uses the Mifflin-St Jeor equation, published in 1990. A 2005 systematic review of the common equations found it the most reliable of them for healthy adults:

BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) + 5    (men)
BMR = 10 × weight (kg) + 6.25 × height (cm) − 5 × age (years) − 161  (women)

2. Maintenance (TDEE) multiplies BMR by an activity factor, from 1.2 for mostly sitting to 1.9 for hard daily training plus a physical job. This is the least precise step: most people aren’t sure how active they are, which is why the apps adjust it from your measured burn instead.

3. Goal. A cut starts 20% below maintenance and a bulk 10% above. These are starting points. Watch your weight for two to three weeks and adjust by small steps if it isn’t moving the way you want.

4. Macros. Protein is set first, in grams per kilogram of bodyweight. The International Society of Sports Nutrition’s position stand cites roughly 1.4 to 2.0 g/kg a day for people who exercise; the default here is 1.8. Fat is a share of calories (25% by default). Carbs fill whatever is left:

protein (g) = g per kg × weight (kg)
fat (g) = target kcal × fat % ÷ 9
carbs (g) = (target kcal − protein × 4 − fat × 9) ÷ 4

What it can’t do

Any equation is an estimate for a typical person. It doesn’t know your body composition, your job or your history, and it isn’t medical advice. If you’re pregnant, under 18, managing a medical condition or have a history of disordered eating, talk to your doctor before changing how you eat.

Built and Shaped start from the same kind of calculation, then adjust it by your measured burn from Apple Health rather than a self-reported activity guess. Next: find meals that fit your numbers with the meal match tool, or read how to use meal delivery on a cut or a bulk.

Macro calculator

The math, with your numbers

How this calculator works

What it can’t do

Sources