What formula does this BMI calculator use?

Body mass index = weight in kilograms ÷ (height in metres)². The categories (underweight, healthy weight, overweight, obesity classes I–III) follow the World Health Organization's standard adult BMI classification, the same cutoffs CDC.gov and most public-health bodies use.

Does this work for children or teenagers?

No. Pediatric BMI is assessed against age- and sex-specific growth-chart percentiles, not the fixed adult cutoffs used here — this tool is for adults only.

Why isn't BMI a great measure for everyone?

BMI uses only height and weight, so it can't distinguish muscle from fat — a very muscular person can show as 'overweight' despite low body fat, and it doesn't account for where fat is distributed, which matters more for health risk than the number alone. Pair it with a body fat or waist-to-height measurement for a fuller picture.

Is a 'healthy weight range' the same as my ideal weight?

It's the weight range that keeps your BMI inside 18.5–24.9 at your current height — a population-level band, not a personalized target. Frame size, muscle mass and individual health goals can reasonably place your best weight above or below it.

BMI Calculator

Calculate adult BMI in metric or imperial units, see your WHO weight category, and get the healthy-weight range for your height — with its real limits explained.

Loading tool…

Formula: BMI = weight(kg) ÷ height(m)²; categories per WHO adult classification (Underweight <18.5, Healthy 18.5–24.9, Overweight 25–29.9, Obesity I 30–34.9, II 35–39.9, III ≥40)

Worked examples

Metric: 180 cm, 75 kg
A result inside the WHO 'healthy weight' band, the most common lookup on this tool.
Metric: 165 cm, 95 kg
A result in the obesity range, showing the class I/II/III sub-bands this tool reports rather than one blanket 'obese' label.
Imperial: 70 in, 160 lb
The same WHO formula entered in US customary units, returning the healthy weight range in pounds.

What this calculator does

This tool calculates body mass index (BMI) from your height and weight, in either metric or imperial units, and classifies the result using the World Health Organization's standard adult BMI categories. It also shows the healthy-weight range — the span of weights that would put you inside the WHO "healthy weight" band at your current height — so you can see the target range, not just a single number.

The calculation

BMI = weight in kilograms ÷ (height in metres)². This formula, first proposed by Adolphe Quetelet in the 19th century and later adopted as a population health-screening tool, produces a single number used to bucket adults into WHO's five weight categories: underweight (below 18.5), healthy weight (18.5–24.9), overweight (25–29.9), and obesity classes I, II and III (30–34.9, 35–39.9, and 40 and above). These are the same cutoffs used by CDC.gov and most public-health agencies worldwide, which is why BMI is so widely reported despite its real limitations.

Why this isn't the hub's lead tool

BMI is one of the most heavily searched fitness terms online, but Google's own in-search BMI widget and CDC.gov's calculator already dominate that specific query — there's little room for another generic BMI page to add anything new. This tool exists mainly for completeness and to link naturally to the hub's more diagnostic body-composition tools, like the body fat and waist-to-height ratio calculators, rather than as a page meant to compete head-on for the bare "bmi calculator" search term.

Limits — what BMI doesn't measure

BMI uses only height and weight, so it cannot tell muscle from fat. A muscular athlete and a sedentary person of the same height and weight get an identical BMI, even though their health profiles differ substantially — a well-known limitation acknowledged even by the WHO's own guidance. BMI also says nothing about where fat is carried on the body, and abdominal fat carries different health implications than fat distributed elsewhere, which is one reason waist-based measurements are often used alongside it. It doesn't adjust for age, sex-specific body composition differences, bone density, or ethnicity-specific risk thresholds that some public health bodies now recommend adjusting for. This calculator is built for adults only — pediatric BMI is assessed against age- and sex-specific growth-chart percentiles, a completely different clinical framework that this tool does not attempt to replicate.

How to use the result

Treat your BMI category as a rough screening signal, not a diagnosis. If your number falls outside the healthy-weight band, that's a reasonable prompt to look more closely — ideally with a body composition measurement that accounts for muscle mass — rather than a number to act on by itself.

This tool gives a general estimate from a published formula. It is not medical advice; talk with a qualified healthcare professional before making decisions about your weight or health based on this or any other calculator.

Frequently asked questions

What formula does this BMI calculator use?: Body mass index = weight in kilograms ÷ (height in metres)². The categories (underweight, healthy weight, overweight, obesity classes I–III) follow the World Health Organization's standard adult BMI classification, the same cutoffs CDC.gov and most public-health bodies use.
Does this work for children or teenagers?: No. Pediatric BMI is assessed against age- and sex-specific growth-chart percentiles, not the fixed adult cutoffs used here — this tool is for adults only.
Why isn't BMI a great measure for everyone?: BMI uses only height and weight, so it can't distinguish muscle from fat — a very muscular person can show as 'overweight' despite low body fat, and it doesn't account for where fat is distributed, which matters more for health risk than the number alone. Pair it with a body fat or waist-to-height measurement for a fuller picture.
Is a 'healthy weight range' the same as my ideal weight?: It's the weight range that keeps your BMI inside 18.5–24.9 at your current height — a population-level band, not a personalized target. Frame size, muscle mass and individual health goals can reasonably place your best weight above or below it.

These calculators give general estimates from published formulas. They are not medical advice and do not account for your individual health; talk to a qualified professional before changing your diet or training.