BMI is a quick screening tool, not a diagnosis. It doesn't distinguish muscle from fat or account for age, sex or body composition. Talk to a healthcare professional about what's right for you.
Body mass index is a simple ratio of weight to height that's widely used to place adults into broad weight categories. It's easy to calculate and useful for looking at populations, but for any individual it's only a starting point — it can't tell muscle from fat or show where weight is carried. This calculator gives your BMI, the standard category, and the weight range considered healthy for your height.
How BMI is calculated
BMI divides your weight by the square of your height. In metric it's kilograms over metres squared; in imperial there's a conversion factor of 703.
Because BMI uses only height and weight, very muscular people can score as "overweight" despite low body fat, while others in the healthy range may carry more fat than is ideal. It also doesn't reflect age, sex, ethnicity or where fat is stored — waist measurement and body-fat percentage add useful context. Use BMI as one signal among several, and speak with a healthcare professional before making changes based on it.
Frequently asked questions
What is a healthy BMI?
For most adults, a BMI between 18.5 and 24.9 is considered the healthy-weight range, though it's only a general guide.
Is BMI accurate for athletes?
Not always. Muscle weighs more than fat, so very muscular people can have a high BMI while carrying little fat. Body-fat measures are more informative for them.
Does BMI work for children?
Children and teens use age- and sex-specific BMI percentiles rather than the adult categories here. Use a paediatric tool for under-18s.
Should I worry about my BMI?
BMI is a screening tool, not a diagnosis. If you have concerns about your weight or health, a doctor can give personalised advice.
For general information only, not medical advice. BMI is a screening tool with real limitations and doesn't diagnose health or body composition. Consult a qualified healthcare professional about your individual health.
Written by the CalcPine team · Reviewed for accuracy · Last updated 13 July 2026 · Method: BMI = weight ÷ height² (metric), or 703 × lb ÷ in² (imperial), with standard adult categories.
