The Fitness Body Mass Index Calculator computes body mass index, or BMI, from height and weight. BMI is a screening ratio that can be useful for broad comparisons, population analysis, or tracking changes when the same measurement method is used. The result includes the BMI value and a general adult category. BMI does not directly measure body fat, muscle mass, bone density, fat distribution, or health. Athletes, older adults, pregnant people, children, and individuals with unusual body composition may need a different interpretation.
Use kilograms and a recent measurement when possible.
Use standing height in centimeters without shoes.
The main result is weight divided by height squared.
Treat the category as a screening reference, not a diagnosis or direct body-fat measurement.
BMI = Weight (kg) ÷ Height (m)²
Height in centimeters is divided by 100 before squaring. The displayed category uses common general adult cutoffs: below 18.5, 18.5–24.9, 25.0–29.9, and 30.0 or higher.
BMI expresses body weight relative to height and provides a broad screening value.
A clinician can interpret BMI alongside age, body composition, medical history, and other measurements.
Given: Weight 70 kg and height 175 cm.
Calculation: Height = 1.75 m. BMI = 70 ÷ (1.75 × 1.75) = 22.86.
Result: BMI is 22.9, which falls in the general adult “healthy weight” range.
No. BMI uses only height and weight, so it cannot distinguish fat mass from muscle, bone, or water.
No. BMI for children and adolescents is interpreted using age- and sex-specific growth references.
Higher muscle mass can increase body weight without the same health meaning as excess body fat.
Either can be used, but consistent timing and conditions make trend comparisons more meaningful.
Use it as one screening data point. Health decisions should consider additional measurements and professional guidance when appropriate.