Does BMI differ between men and women?

The calculation and category thresholds are the same for both sexes, even though body composition tends to differ — women typically carry more essential body fat than men at an equivalent BMI. That's one reason it's worth pairing BMI with another measure rather than reading it alone.

Does BMI apply to children the same way?

The formula is the same, but the interpretation isn't — children and teens are assessed against age- and sex-specific percentile growth charts rather than the fixed adult ranges shown here, since healthy body fat naturally changes as kids grow.

Can someone be healthy with a BMI outside the 'normal' range?

Yes. BMI is one data point among many — blood pressure, blood sugar, cholesterol, muscle mass, and lifestyle all matter and aren't captured by a height-and-weight ratio. A single out-of-range result isn't cause for alarm on its own.

A BMI of 26 falls just inside the 'overweight' range (25.0–29.9), a screening category rather than a diagnosis. On its own it isn't cause for alarm — it's worth discussing with a clinician alongside other factors like waist circumference, activity level, and family history.

Why does WHO use different BMI cutoffs for some populations?

WHO's Western Pacific Regional Office recommends lower overweight/obesity cutoffs for Asian populations (23 and 25, instead of 25 and 30), since research has found higher health risks at lower BMI values in these groups. This calculator uses the standard global cutoffs shown above.

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Health & Fitness

BMI Calculator

Body mass index with WHO weight category.

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About the BMI Calculator

Body Mass Index estimates whether your weight falls in a healthy range for your height, using the same formula used for adult population health screening worldwide. It's a quick screening number, not a diagnosis — most useful as a starting point rather than a complete picture of health.

How to use it

Choose your unit system in the Units field — Metric (cm / kg) or Imperial (in / lb).
Enter your height in the Height field.
Enter your weight in the Weight field.
Read your BMI and weight category instantly in the result panel — it updates as you type, with the gauge below showing where you fall across the full range.

Formula

BMI = weight (kg) ÷ height (m)²
Imperial: BMI = 703 × weight (lb) ÷ height (in)²

Known as the Quetelet Index after Belgian statistician Adolphe Quetelet, who devised it between 1830 and 1850; physiologist Ancel Keys renamed it "Body Mass Index" in a 1972 paper, and it's the formula WHO uses for adult population screening today.

Worked example

A person 175 cm tall weighing 70 kg: 70 ÷ (1.75 × 1.75) = 22.9, which falls in the 'normal' range of 18.5–24.9.

Adult BMI categories (WHO standard)

BMI range	Category
Below 18.5	Underweight
18.5 – 24.9	Normal weight
25.0 – 29.9	Overweight
30.0 and above	Obese

Interpreting your result

BMI is a screening measure, not a health verdict. It can't distinguish muscle from fat, doesn't account for where on the body weight is carried, and its standard ranges were developed primarily from adult population studies — so results can be misleading for athletes, older adults, and some ethnic groups with different risk thresholds. If your result concerns you, a healthcare provider can put it in context alongside other measures.

Recommendations

• Track BMI over time rather than fixating on any single reading — the trend matters more than one number.
• Measure at a similar time of day for consistency, since weight can fluctuate a few pounds within a day.
• Pair BMI with a waist or body-fat measurement for a fuller picture, especially if you're very active or muscular.

Frequently asked questions

It's a population-level screening tool, not an individual diagnosis. It doesn't distinguish muscle from fat, so athletic or very muscular people are often classified 'overweight' despite low body fat. For a more specific estimate, try the Body Fat Calculator.

Related tools

Body Fat Calculator

Ideal Weight Calculator

Calorie Calculator

Sources

WHO — Obesity and overweight (fact sheet) — accessed 2026-08-19
WHO Global Health Observatory — Body mass index (adults) — accessed 2026-08-19
Wikipedia — Body mass index (Quetelet/Keys history) — accessed 2026-08-19

Disclaimer

Educational estimate, not medical advice. Consult a qualified clinician before making health decisions.