Basal metabolic rate (BMR) is the daily energy the body uses at rest for vital functions; it makes up 60–70% of total expenditure. It is estimated from age, sex, height and weight with the Mifflin-St Jeor equation, with a margin of about ±10%. BMR multiplied by an activity factor gives total daily energy expenditure (TDEE); for healthy weight loss intake should be 300–500 kcal below TDEE but never below BMR.
How should you read your result?
BMR is the energy you burn even if you don't move at all. TDEE is your total expenditure including daily activity; to maintain weight you need roughly this many calories. To lose weight you aim below TDEE but above BMR. The calculator gives this safe range automatically.
Limits of the formula
- It does not measure muscle mass directly; in muscular people the true BMR is higher.
- Thyroid disease, pregnancy, breastfeeding and some medications change the value.
- In people with a long history of very-low-calorie dieting the true BMR may be lower than the formula (adaptive thermogenesis).
That is why at the office I measure your muscle-to-fat ratio with body composition analysis and build the programme on that real data. For details see metabolism-focused nutrition.
Frequently asked questions
What is basal metabolic rate (BMR)?
BMR is the daily energy your body uses at complete rest for vital functions such as breathing, circulation and cell renewal. It makes up roughly 60–70% of your total energy expenditure and is affected by muscle mass, age, sex, height, weight and hormonal status.
Which formula does the calculator use?
The Mifflin-St Jeor equation (1990): Men = 10×weight + 6.25×height − 5×age + 5; Women = 10×weight + 6.25×height − 5×age − 161. It is recommended by the Academy of Nutrition and Dietetics as the most accurate predictive equation in clinical practice, with a margin of about ±10%.
Will I lose weight faster if I eat below my BMR?
In the short term yes, in the long term no. Eating below BMR for long periods causes muscle loss and adaptive thermogenesis (metabolic slowdown); weight plateaus and is regained. A safe deficit is 300–500 kcal below TDEE and never below BMR.
My result is low; is my metabolism slow?
The formula does not measure muscle mass directly; a muscular person of the same weight has a higher true BMR. A low result usually points to correctable causes such as low muscle mass, long-term restrictive dieting or thyroid issues. Body composition analysis gives the exact value.