What to eat
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Body composition
BMI Calculator
Body Mass Index estimates whether your weight is in a healthy range for your height. Enter your details to see your BMI, category, and a healthy weight range.
What your BMI does and doesn't tell you
Body Mass Index (BMI) is a quick screening number that compares your weight to your height. It is calculated as weight in kilograms divided by height in metres squared. Because it takes seconds to work out and needs no special equipment, health services use it to flag whether an adult may be underweight, a healthy weight, overweight, or living with obesity.
The value is useful at a population level, but it has real limits for individuals. BMI does not distinguish muscle from fat, so very muscular people can read as "overweight" even with low body fat. It also says nothing about where fat is stored — carrying weight around the waist carries more health risk than the same weight on the hips and thighs. For these reasons, treat BMI as one signal among several rather than a verdict on your health.
How to read your BMI category
- Under 18.5 — underweight. May signal undernutrition or an underlying condition worth discussing with a clinician.
- 18.5 to 24.9 — healthy weight. Associated with the lowest risk for most adults.
- 25 to 29.9 — overweight. A cue to look at habits; a small, steady change often moves the number.
- 30 and above — obese. Linked to higher risk of type 2 diabetes, heart disease, and joint problems.
If your number sits near a boundary, don't over-read a single decimal point — day-to-day weight shifts with hydration and food. Track the trend over weeks instead. To go deeper, combine BMI with a waist measurement, a body-fat percentage estimate, and how you feel day to day.
Categories follow WHO and U.S. CDC adult BMI classifications. See CDC, "About Adult BMI," and NHS, "BMI healthy weight calculator."
Frequently asked questions
What is a healthy BMI?
For most adults a BMI between 18.5 and 24.9 is classed as a healthy weight. Below 18.5 is underweight, 25 to 29.9 is overweight, and 30 or above is obese. These bands come from the World Health Organization and CDC and apply to adults aged 20 and over.
Is BMI accurate for athletes and muscular people?
Not always. BMI only compares weight to height and cannot tell muscle from fat, so a very muscular person can register as overweight while carrying little fat. If you train seriously, pair BMI with a body-fat estimate and a waist measurement for a fuller picture.
How do I lower my BMI?
Because BMI is driven by weight and height, lowering it means losing body weight through a modest, sustained calorie deficit combined with activity. Our TDEE calculator estimates how many calories you burn per day so you can set a realistic target.
Is BMI calculated differently for men and women?
No. The BMI formula and adult categories are the same for men and women. Body composition does differ between sexes, which is one reason BMI is a screening tool rather than a diagnosis.
Does BMI work for children?
Children and teens use age- and sex-specific BMI percentiles rather than the fixed adult bands, so this calculator is intended for adults aged 20 and over.
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