Basal Metabolic Rate.
These calculators use established formulas (such as Mifflin-St Jeor for calorie needs or the Devine formula for ideal weight) to provide general estimates. They're built for a general population and don't account for individual medical conditions, medications, or circumstances. They aren't a substitute for advice from a doctor, registered dietitian, or other qualified healthcare provider — especially for anything related to pregnancy, chronic conditions, or medication dosing.
BMR is calories you'd burn lying in bed all day. Driven by lean body mass, age, and sex.
Mifflin-St Jeor: 10×kg + 6.25×cm − 5×age + (5 male, −161 female).
BMR naturally declines with age, largely because lean muscle mass tends to decrease over time unless actively maintained through resistance training — this is a big part of why calorie needs shift across decades even at a stable weight.
30-year-old, 175 cm, 70 kg male: BMR = 700 + 1093.75 − 150 + 5 = 1,649 kcal/day.
BMR is calories at rest. TDEE adds activity — walking, exercise, digestion — 1.2× to 1.9× BMR.
Modestly — muscle is metabolically active, so resistance training helps offset age-related BMR decline.
Body composition matters more than total weight — someone with more muscle mass burns more calories at rest than someone the same weight with a higher fat percentage.