Mifflin-St Jeor — the formula most major dietitian and sports-nutrition bodies recommend for healthy adults because it tracks measured resting metabolic rate more closely than the older Harris-Benedict equation. For men: BMR = 10 × weight(kg) + 6.25 × height(cm) − 5 × age + 5. For women: same with −161 instead of +5. TDEE is BMR multiplied by an activity factor.
Sedentary (×1.2) is a desk job with no structured exercise. Lightly active (×1.375) is 1–3 light sessions a week or lots of walking. Moderately active (×1.55) is 3–5 moderate sessions a week. Very active (×1.725) is 6–7 hard sessions a week or a physical job. Extra active (×1.9) is twice-a-day training or heavy manual labor. Most people overestimate by a level — when in doubt, pick one lower for a fortnight and adjust based on the scale.
Protein is set per kilogram of bodyweight: 2.2 g/kg on a cut to spare muscle, 1.8 g/kg on maintenance, 1.8 g/kg on a lean bulk. Fat is set as a percentage of total kcal: 25% on a cut, 30% on maintenance, 25% on a bulk. Carbohydrate fills the remaining calories. 1 g protein and 1 g carbohydrate = 4 kcal, 1 g fat = 9 kcal — the per-day grams are derived from the goal-adjusted kcal target.
Each goal shifts your TDEE up or down by a fixed daily deficit or surplus: −500 kcal/day for a 1 lb/week cut, −250 kcal/day for a 0.5 lb/week cut, 0 for maintenance, +250 kcal/day for a 0.5 lb/week lean bulk, +500 kcal/day for a 1 lb/week bulk. The 3,500 kcal-per-pound rule of thumb is an approximation — real-world rate of loss or gain varies with adherence, water weight, and metabolic adaptation, so re-check progress every 2–4 weeks.
Every 4–6 weeks, or any time your weight changes by 5 kg or more. As your body composition changes, your BMR changes with it — the formula's inputs shift, so the output should too. Most people on a cut hit a plateau not because their body has stopped responding but because they haven't updated their target as they've lost weight.
No — only the input units. Internally everything is converted to kilograms and centimetres before BMR runs, so switching from lb/in to kg/cm and back gives the same result (to within the rounding of a single decimal place). The toggle is a display preference; the numbers underneath are identical.
No. Age, sex, height, weight, activity level, and goal stay in your browser. There is no signup, no profile, no server-side storage. The inputs are encoded into the URL hash (the part after #) so you can bookmark or share the page and reopen the exact same result — that hash never leaves your device unless you copy and send the link yourself.
No. The numbers are population-average estimates suitable for general fitness and weight management. They are not a substitute for advice from a registered dietitian or doctor — particularly if you have a medical condition, are pregnant or breastfeeding, are under 18, or are recovering from an eating disorder. Consult a qualified professional before making large changes to your diet.