Health Calculator
BMI Calculator.
Enter your height and weight to get your Body Mass Index and WHO health category instantly.
About BMI
What does your BMI actually tell you?
Body Mass Index is a screening tool that estimates body fatness from height and weight. The formula is simple: weight (kg) ÷ height (m²). A result between 18.5 and 24.9 falls in the WHO healthy range for most adults.
BMI is useful because it's fast and requires no equipment — which is why it's used by the WHO and most public health agencies for population-level screening. However it has real limitations: it doesn't distinguish muscle from fat, and it can misclassify athletic individuals as overweight.
3–10 years
reduction in life expectancy associated with obesity (BMI ≥ 30), according to research cited in the Lancet.
The most health-relevant range to watch isn't the borderline — it's the bottom and top. A BMI below 18.5 is associated with nutritional deficiencies and weakened bone density. A BMI above 30 meaningfully increases risk of cardiovascular disease, type 2 diabetes, and certain cancers.
For a fuller picture, use your BMI alongside our Life Expectancy Calculator — which factors in your BMI as one of 10+ health inputs — and our Heart Age Calculator.
WHO BMI categories
Your measurements
Your result
—
BMI score
Underweight
< 18.5
Normal
18.5–24.9
Overweight
25–29.9
Obese
≥ 30
FAQ
Frequently asked questions.
What is a healthy BMI?
A BMI between 18.5 and 24.9 is considered healthy by WHO standards. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above is classified as obese. These thresholds apply to most adults but may not account for muscle mass or fat distribution.
What is a normal BMI for women?
The healthy BMI range for women is the same as for men: 18.5 to 24.9. However, women typically have a higher percentage of body fat than men at the same BMI, which is normal. WHO thresholds do not differ by sex.
What is a normal BMI for men?
For adult men, a BMI of 18.5 to 24.9 is considered normal weight. A BMI of 25 to 29.9 is overweight, and 30 or above is obese. Men tend to carry less body fat than women at the same BMI due to differences in muscle mass.
Does BMI affect life expectancy?
Yes. A BMI in the obese range (30 and above) is associated with reduced life expectancy, primarily through increased risk of heart disease, type 2 diabetes, certain cancers, and sleep apnea. Research suggests obesity can reduce life expectancy by 3 to 10 years depending on severity.
What are the limitations of BMI?
BMI does not distinguish between muscle and fat, nor does it account for where fat is stored. Athletes can have a high BMI without excess fat. Older adults can have a normal BMI but excess visceral fat. Waist circumference is a useful supplementary measure.
How is BMI calculated?
BMI is calculated by dividing your weight in kilograms by your height in metres squared: BMI = kg / m². In imperial units: BMI = (weight in pounds / height in inches²) × 703.