We estimate resting energy needs using the Mifflin–St Jeor equation: 10 × weight (kg) + 6.25 × height (cm) − 5 × age, then −161 for female or +5 for male. The equation uses a binary sex variable and may not be a good fit for everyone.

We multiply by an estimated activity factor (1.2, 1.375, 1.55, or 1.725). For a starting target, fat loss uses 15% below estimated maintenance, maintenance uses no adjustment, and gradual weight gain uses 5% above maintenance. These activity factors and goal adjustments are practical assumptions, not measured metabolism or guaranteed outcomes.

FFA's coaching starting rule is approximately 1 gram of protein per pound of current body weight, capped at 215 grams per day. For metric inputs, we convert kilograms to pounds first. Fat receives about 30% of calories; carbs receive all remaining calories after protein and fat. Above 215 lb, protein stays at 215 grams instead of continuing to rise. The protein cap does not reduce your calorie target: those calories remain available for carbs. Targets are rounded to whole grams, so macro calories may differ slightly from the displayed total. This is FFA's coaching approach, not a universal medical requirement.

We don't generate targets for underweight inputs (BMI below 18.5), unusually low estimated intakes (below 1,200 for female or 1,500 for male), inputs outside this tool's limits, or combinations that leave less than 50 grams of carbs after protein and fat. These are screening guardrails, not individual safety thresholds. If you have a medical condition, an eating-disorder history, or needs affected by medication, ask a registered dietitian or clinician for individualized guidance.