Body Mass Index calculator
The BMI calculator returns body mass index in kg/m2 from weight and height, along with the standard World Health Organization category. Weight can be entered in kilograms or pounds and height in centimetres, so it fits whichever units your unit charts in.
The formula and the bands
BMI = weight (kg) / height (m)2. The conventional adult bands are: under 18.5 underweight, 18.5 to 24.9 normal, 25.0 to 29.9 overweight, and 30.0 and above obese.
A worked example
A patient weighing 82 kg at 175 cm: 1.75 squared is 3.0625, and 82 / 3.0625 = 26.8 — in the overweight band.
What BMI does not measure
BMI does not distinguish muscle from fat, says nothing about where body fat sits, and is unreliable for very muscular people, older adults with reduced muscle mass, pregnant patients and children, who need age-and-sex-specific percentile charts instead.
It is a population screening measure that became a bedside habit. Treat it as one data point beside the actual assessment.
What this does not do
This is an adult calculation. It does not apply paediatric percentiles, does not adjust for pregnancy, ethnicity or body composition, and does not assess nutritional status or health risk. It converts or computes a number and stops there. Interpreting it is your job, alongside your own assessment and your institution guidance.
Frequently asked questions
Can I use pounds and inches?
Weight can be entered in pounds and is converted automatically. Height is entered in centimetres — multiply inches by 2.54.
Does BMI work for children?
No. Children need age-and-sex-specific percentile charts, not the adult bands.
Is BMI reliable for athletes?
Often not. Muscle is dense, so a very muscular person can land in the overweight or obese band with low body fat.
By The Nursana team · Last updated · Canonical: https://nursana.aoneahsan.com/tools/bmi
Nursana provides reference tools only and does not give medical, legal or tax advice.