BMI / BMR
Understanding BMI, BMR and TDEE
BMI compares weight with height, while BMR estimates energy used at rest. TDEE multiplies BMR by an activity factor to estimate daily energy use. These screening estimates are not diagnoses and can be less informative for children, pregnancy, older adults, and very muscular people.
Formula and method
BMI = weight in kilograms ÷ height in meters squared. BMR uses the Mifflin–St Jeor equation; TDEE = BMR × activity factor.
Worked example
At 70 kg and 170 cm, BMI is approximately 24.2. Interpretation should consider health history and body composition.
How to interpret the result
BMI is a screening ratio, not a direct measurement of body fat or health. BMR estimates resting energy expenditure from age, height, weight, and the sex term used by the Mifflin–St Jeor equation. TDEE then applies a broad activity multiplier, so it is best treated as a starting estimate that can be adjusted using observed weight trends.
Important limitations
- Consult a qualified clinician for health decisions.
- Activity factors are broad estimates.
Common questions
Can BMI diagnose whether someone is healthy?
No. BMI does not account for muscle mass, pregnancy, body-fat distribution, or individual medical history. A clinician can interpret it alongside other measurements and risk factors.
Why does actual calorie use differ from TDEE?
Activity categories summarize many different routines into a few multipliers. Sleep, training volume, occupation, health, and measurement error can all move actual energy use away from the estimate.
Source and further reading
Related tools
Method and examples reviewed September 8, 2026.