BMI Calculator
Body Mass Index (BMI) is a simple screening measure that relates your weight to your height. It is used by health organizations worldwide to sort adults into broad categories: underweight, normal weight, overweight, and obesity. Enter your height and weight below, in metric or imperial units, to get your BMI and category instantly.
- Your BMI
- 22.9
- Category
- Normal weight
- Normal BMI range
- 18.5 – 24.9
BMI is a population-level screening tool, not a diagnosis. It does not distinguish muscle from fat, so very muscular people can score as overweight while carrying little fat. Treat it as one signal among many, alongside waist circumference, fitness, and advice from a healthcare professional.
How it's calculated
BMI = weight (kg) ÷ height² (m²)
With imperial units the equivalent is BMI = 703 × weight (lb) ÷ height² (in²). The standard adult categories defined by the WHO are: under 18.5 underweight, 18.5–24.9 normal, 25–29.9 overweight, and 30 or above obesity.
Worked example
Someone who is 175 cm (1.75 m) tall and weighs 70 kg has a BMI of 70 ÷ 1.75² = 22.9, which falls in the normal range. The same person at 80 kg would have a BMI of 26.1, which is in the overweight range.
Frequently asked questions
›What is a healthy BMI?
For most adults, the World Health Organization defines the normal range as 18.5 to 24.9. Ranges can differ slightly by population; some Asian countries use lower cutoffs for overweight and obesity.
›Is BMI accurate for athletes?
Often not. Muscle is denser than fat, so muscular athletes frequently have a high BMI despite low body fat. Body-composition measurements give a truer picture in that case.
›Does BMI apply to children?
Not with these adult cutoffs. Children and teens are assessed with age- and sex-specific BMI percentile charts, because healthy body composition changes as they grow.
›How can I change my BMI?
Since height is fixed in adulthood, BMI changes with weight. Sustainable changes to diet and physical activity are the standard approach. Consult a doctor before major weight-loss efforts.
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