BMI & Health Calculator

How to use 3 steps

Enter your Weight in kg.
Enter your Height in cm.
Press Calculate BMI and read the range it falls in.

Weight (kg):

Height (cm):

Body Mass Index Result

How this tool works

Enter weight in kilograms and height in centimetres and the result is a body mass index figure with the category the standard adult ranges place it in.

BMI is weight in kilograms divided by height in metres squared. It was devised in the nineteenth century as a way of describing populations, not individuals, and that is still what it does best. The number says nothing about what the weight is made of, where it sits on the body, or anything about the person carrying it, which is why a very muscular athlete and someone carrying excess fat can share a BMI. The categories shown are the standard adult thresholds; they are not a diagnosis and they are not a target.

What the number cannot tell you

Muscle weighs more than fat: a trained athlete frequently lands in the overweight or obese range on BMI alone while being in excellent health. The index cannot distinguish tissue types.
It was never designed for individuals: the formula describes distributions across populations. Applied to one person it is a rough screen, not a measurement of health.
Thresholds vary by population: several health bodies use lower cut-offs for people of South Asian and East Asian descent, because risk profiles differ at the same index value.
It does not apply to everyone: children, pregnant women, older adults and people with significant muscle mass all need different measures. The adult categories are simply the wrong instrument for them.

What BMI was actually built to describe

The [msm_tool slug="bmi-calculator"] divides weight in kilograms by the square of height in metres, a formula devised in the nineteenth century to describe populations rather than individual people — and describing populations is still what it does best. The categories shown are the standard adult thresholds used for that population-level screening, not a diagnosis and not a target to aim for.

Why an athlete and someone carrying excess fat can share a number

Muscle weighs more than fat for the same volume, and the formula has no way to distinguish one tissue type from the other — it only ever sees total weight against height. A trained athlete frequently lands in the overweight or obese range on BMI alone while being in excellent health, simply because the index cannot see what the weight is actually made of.

The same number does not mean the same risk everywhere

Several health authorities apply lower BMI thresholds for people of South Asian and East Asian descent, because the relationship between this particular index and actual health risk genuinely differs across populations at the same numeric value. A single set of adult categories was never going to fit everyone equally well.

Whole groups of people fall outside what it measures

Children are assessed against age-and-sex percentile charts rather than the adult categories shown here, BMI is not a meaningful measure during pregnancy at all, and older adults and people carrying significant muscle mass are all cases where the standard adult thresholds are simply the wrong instrument to reach for.

A starting point for a conversation, not a verdict

The figure ignores body composition, fat distribution, fitness, diet and medical history entirely, and it misclassifies muscular people in a routine, predictable way. Any real concern about weight or health is worth raising directly with a doctor or another qualified professional who can actually look at the whole picture, rather than settling the question from this number alone.

Frequently Asked Questions

Specific to the BMI & Health Calculator. Broader questions about this category are answered on the category page.

How is BMI calculated?

Weight in kilograms divided by the square of height in metres. Using centimetres, divide the height by a hundred first. The arithmetic is the easy part; interpreting the result is where the care is needed.

Is BMI a reliable measure of health?

Only as a rough screen at population level. It ignores body composition, fat distribution, fitness, diet and medical history, and it misclassifies muscular people routinely. A clinician looking at you can weigh all of that; a single ratio cannot.

Why do some countries use different thresholds?

Because the relationship between BMI and health risk differs across populations. Several health authorities apply lower cut-offs for people of South and East Asian descent, where metabolic risk appears at a lower index value.

Does BMI apply to children or during pregnancy?

No. Children are assessed against age and sex percentile charts, and BMI is not a meaningful measure during pregnancy. The categories shown here are adult thresholds only.

Should I act on this number?

Not on its own. If you have a concern about your weight or health, that is a conversation with a doctor or another qualified professional who can look at the whole picture. This figure is a starting point for that conversation, not a substitute for it.