Your body uses energy all day, even when you are sitting still. Two terms help explain where it goes: BMR and TDEE. Understanding them makes calorie estimates far less mysterious.
What is BMR?
Basal metabolic rate (BMR) is the energy your body uses at rest to run basic functions such as breathing, circulation, temperature control and cell repair. For most people it accounts for the majority of the calories they burn each day. It depends on your weight, height, age and sex, and on things like muscle mass.
What is TDEE?
Total daily energy expenditure (TDEE) is your BMR plus everything else: movement, exercise and the energy used to digest food. It is the number of calories that would keep your weight stable.
How it is calculated
The Mifflin-St Jeor equation estimates BMR from your weight in kilograms, height in centimeters and age in years:
Women: 10 × kg + 6.25 × cm − 5 × age − 161
You then multiply by an activity factor to estimate TDEE:
| Activity level | Multiplier |
|---|---|
| Sedentary: desk job, little exercise | 1.2 |
| Lightly active: exercise 1 to 3 days a week | 1.375 |
| Moderately active: 3 to 5 days a week | 1.55 |
| Very active: 6 to 7 days a week | 1.725 |
| Extra active: hard training or physical job | 1.9 |
Example
A 35-year-old woman, 65 kg and 165 cm:
TDEE (lightly active) = 1,345 × 1.375 = about 1,850 calories
A 30-year-old man who is 80 kg and 180 cm and exercises 3 to 5 days a week would have a BMR of 1,780 and a TDEE of around 2,760.
Using your number sensibly
- It is an estimate. Two people with the same stats can differ by several hundred calories.
- Be honest about activity. Most people overestimate how active they are. If in doubt, choose the lower level.
- Test it. Eat near your estimate for two to three weeks while tracking your weight. Stable weight suggests you are close to maintenance.
- Change slowly. Small adjustments of roughly 250 to 500 calories a day are commonly used for gradual change. The idea that 3,500 calories equals a pound is only a rule of thumb, because metabolism adapts.
- Do not go extremely low. Very low calorie diets need medical supervision.
What calorie estimates cannot tell you
Calories are only part of the picture. Food quality, protein, fibre, sleep, stress and medical conditions all affect health and weight. If you are unsure how to eat for your goals, or have a health condition or a history of disordered eating, speak with a doctor or registered dietitian.
Try your own numbers in the calorie calculator. To see where your weight sits on a standard screening scale, use the BMI calculator. This article is general information and not medical advice.