BMI Calculator
Check your Body Mass Index and see where you fall on the scale.
Your result
Enter your details and press calculate to see your result.
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Body Mass Index (BMI) is a single number that relates your weight to your height, used as a quick screen for whether you sit in a healthy weight range. It does not measure body fat directly, but it correlates well enough with it across large populations to be the standard first check used by doctors and health agencies. This calculator takes your height and weight in metric or imperial units, returns your BMI, and places you on a colour-coded scale from underweight to obese so you can see your category at a glance.
How BMI is calculated
The formula is your weight in kilograms divided by your height in metres squared: BMI = kg / m2. If you enter imperial units, the calculator converts them first. For example, someone who weighs 70 kg at 175 cm has a height of 1.75 m, so 1.75 squared is 3.0625, and 70 divided by 3.0625 gives a BMI of 22.9. That falls in the normal range.
The categories come from the World Health Organization classification: below 18.5 is underweight, 18.5 to 24.9 is a normal or healthy weight, 25.0 to 29.9 is overweight, and 30.0 and above is obese. The same formula and the same thresholds apply to adult men and women alike.
What your BMI category means
A normal BMI is linked to the lowest average risk of weight-related conditions, while the underweight, overweight and obese bands are associated with higher risk on a population level. Use the result as a flag, not a diagnosis: it tells you whether a closer look is worthwhile, not what your body is made of.
BMI has a well-known blind spot. Because it uses only height and weight, it cannot tell muscle from fat, so a lean, muscular athlete can read as overweight while a person with little muscle can read as normal while carrying excess fat. It also says nothing about where fat sits on your body. For a fuller picture, pair BMI with a body-fat percentage estimate or a waist-to-height ratio.
BMI for different groups
The standard cut-offs apply to adults aged 20 and over. Children and teenagers are assessed with age- and sex-specific percentile charts instead of fixed numbers, so this calculator is not meant for them. Some health bodies also use lower thresholds for people of South Asian descent, where weight-related risk rises at a lower BMI. If your number sits near a boundary or you are very muscular, treat it as a starting point and discuss it with a clinician rather than reading the band as a verdict.
How to use
- 01
Enter height and weight
Switch between metric and imperial and type your measurements.
- 02
Calculate
Your BMI appears instantly with its WHO category.
- 03
Read the scale
The marker shows exactly where you sit between underweight and obese.
Frequently Asked Questions
A BMI between 18.5 and 24.9 is classified as a normal, healthy weight by the World Health Organization.
Not always. BMI does not distinguish muscle from fat, so very muscular people can read as "overweight" while being lean. Use body-fat percentage for a fuller picture.
BMI = weight in kilograms divided by height in metres squared (kg/m²).
The formula and categories are the same, but at the same BMI women typically carry more body fat than men.
Reference data
| Category | Range (kg/m²) |
|---|---|
| Underweight | < 18.5 |
| Normal Weight | 18.5 – 25 |
| Overweight | 25 – 30 |
| Obese | ≥ 30 |
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Last reviewed June 2026 · Methodology & sources