Calculate your Basal Metabolic Rate (BMR) — the number of calories your body needs at rest — using three different formulas. Results shown in both kcal and kJ (as used on Australian food labels).
| Formula | BMR (kcal) | BMR (kJ) | TDEE (kcal) |
|---|
| Activity Level | kcal/day | kJ/day |
|---|
Your Basal Metabolic Rate (BMR) is the energy your body needs to maintain vital functions at complete rest — breathing, circulation, cell production, and temperature regulation. It accounts for 60–75% of total daily energy expenditure for most people.
The Mifflin-St Jeor equation (1990) is generally considered the most accurate for most people and is recommended by the Academy of Nutrition and Dietetics. The Katch-McArdle formula is most accurate for lean individuals who know their body fat percentage, as it accounts for lean body mass.
Australian food labels display energy in kilojoules (kJ). The conversion is: 1 kcal = 4.184 kJ. The average Australian adult daily energy intake is approximately 8,700 kJ (2,080 kcal) for men and 7,100 kJ (1,697 kcal) for women, though individual requirements vary widely.
Age (BMR decreases ~2% per decade after 20), muscle mass, body size, hormones (thyroid), temperature, diet composition, and genetics all influence BMR. Building muscle through resistance training is one of the most effective ways to increase BMR long-term.
The NHMRC publishes Estimated Energy Requirements (EERs) for Australians by age, sex, and physical activity level. These are used as reference values for dietary planning and are based on doubly-labelled water studies.