Health

BMI Calculator

Calculate your Body Mass Index with metric or imperial inputs and quickly see your weight category.

Enter your height and weight to calculate BMI.

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BMI Formula Explained

Body Mass Index estimates body weight status using your height and weight. It is a screening metric, not a full diagnosis.

Metric

BMI = weight(kg) / height(m)^2

Imperial

BMI = (weight(lb) / height(in)^2) x 703

What is BMI?

Body Mass Index (BMI) is a simple measurement of body size based on your height and weight. It’s calculated by dividing weight in kilograms by height in metres squared, and is used worldwide as a screening tool to identify potential weight-related health risks.

BMI categories help classify adults as underweight, normal weight, overweight, or obese. While BMI is useful for population-level screening, it does not directly measure body fat and may not be accurate for athletes, children, older adults, or people with certain body compositions.

Frequently asked questions

What is a healthy BMI range?
For most adults, a BMI between 18.5 and 24.9 is considered healthy. BMI under 18.5 is classified as underweight, 25–29.9 as overweight, and 30 or above as obese according to standard WHO classifications.
Is BMI accurate for everyone?
BMI is a screening tool and does not directly measure body fat. Athletes, older adults, and some body types may need additional measures.
Can I use BMI for children?
Children and teens use BMI-for-age percentiles rather than fixed adult BMI ranges, because healthy weight varies with age and sex during development.
What are the official BMI categories?
The WHO defines four adult BMI categories: underweight (below 18.5), normal weight (18.5–24.9), overweight (25–29.9), and obese (30 and above). Some guidelines add further obesity sub-classes at 35 and 40.
What are the limitations of BMI as a health metric?
BMI does not measure body composition. Athletes with high muscle mass may have a high BMI despite low body fat. Older adults may have a normal BMI but reduced muscle mass. For a fuller picture, BMI should be used alongside waist circumference, body fat percentage, and clinical assessment.

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