BMI Calculator
Your body mass index in seconds, with the category it lands in and the healthy weight range for your height.
Last updated: August 5, 2026
How BMI is calculated
Body mass index compares your weight to your height squared. It was designed as a quick population-level screening tool, and it remains the standard first check for weight-related health risk. The formula divides weight in kilograms by height in metres squared; in imperial units a factor of 703 converts pounds and inches.
The result falls into ranges — underweight, normal, overweight, obese — established by public health bodies. The calculator also shows the weight range that corresponds to a normal BMI for your height, which is often the most practical thing people actually want.
The formula
Worked example
A person 5'9" (69 in) weighing 165 lb.
BMI = 703 × 165 ÷ 69² ≈ 24.4 — the top of the normal range, with the healthy range spanning about 127–170 lb.
The formula is the same for everyone, which is its strength and its weakness: it needs no body measurements, but it cannot see the difference between muscle and fat.
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Frequently asked questions
Is BMI the same for men and women?
The adult formula is the same for both sexes, though body composition typically differs. For children and teens, BMI is judged against age- and sex-specific percentile charts rather than adult ranges.
Does BMI work for children?
Not with adult ranges. Pediatric BMI uses percentile charts adjusted for age and sex, because children's bodies change rapidly as they grow. Ask a pediatrician for the right interpretation.
What if my BMI is high but I'm fit?
BMI can misclassify people with high muscle mass. If that's you, a body-composition measurement (or simply where your weight sits around your waist) may be more informative than the BMI number.
BMI is a screening measure, not a diagnosis. Consult a healthcare professional for a full assessment of your health and weight.