Body composition
BMI calculator
Estimate your body mass index from your weight and height, and see what the number means in plain language — with the usual caveats about what BMI can and cannot tell you.
Enter your values above to see your result and what it means.
What is BMI and what does it stand for?
BMI stands for body mass index, a simple ratio of your weight to your height (weight in kilograms divided by height in metres squared). It was designed as a population-level screening number, not a direct measure of body fat or health. Because it uses only two inputs, it gives a quick, standardised category that works the same way for everyone.
What is a healthy BMI range?
The World Health Organization groups BMI into broad bands: underweight, healthy weight, overweight, and obesity. For most adults the "healthy weight" band sits around 18.5 to 24.9, but the exact cut-offs and how they apply to you can vary, so read the category this tool returns alongside any figures on your own medical report. These bands describe statistical risk across groups, not a verdict about any single person.
Is BMI accurate, and what are its limits?
BMI does not distinguish muscle from fat or show where fat is stored, so very muscular people can land in a higher band while carrying little excess fat. It can also read differently across ages, ethnic backgrounds, and during pregnancy. Treat it as one rough signal among many, not a diagnosis, and talk with a clinician who can add context like a waist measurement and blood results.
How is BMI calculated?
The metric formula is weight (kg) divided by height (m) squared; the imperial version multiplies pounds divided by inches squared by 703. This calculator does the arithmetic for you and maps the result onto the WHO category so you do not have to convert units by hand. Seeing the raw number and the band together makes it easier to understand where you fall.
Does a healthy BMI differ for men and women?
The standard adult BMI bands are the same for men and women, so a given number maps to the same category regardless of sex. Body composition does differ on average between sexes, which is part of why BMI is a screening tool rather than a precise body-fat measure. For children and teenagers, BMI is read against age- and sex-specific percentile charts instead of the adult bands.
Frequently asked questions
Is BMI accurate for everyone?
No. BMI is a useful screen at the population level but it does not measure body fat directly and does not account for muscle mass, fat distribution, age, sex, or ethnicity. Athletes and very muscular people are often misclassified. Treat BMI as one signal, not a verdict on your health.
What is a healthy BMI?
For most adults, a BMI between 18.5 and 24.9 is described as the healthy-weight range, where weight-related risk is lowest at a population level. Below 18.5 is underweight; 25–29.9 is overweight; 30 and above is obesity.
Does BMI work for children?
Not in the same way. Children and teenagers are assessed using age- and sex-specific BMI percentiles, not the fixed adult cut-offs. This calculator is for adults; for a child, use a paediatric BMI-percentile tool or ask a clinician.
Should I worry if my BMI is slightly over 25?
A BMI just above 25 is common and is not, by itself, a health problem. What matters more is your waist size and your metabolic markers — blood pressure, glucose, and cholesterol. If those are healthy, a BMI of 26–27 may not need any action beyond your usual habits.