BMI Calculator

Calculate your Body Mass Index (BMI) to estimate whether your weight is in a healthy range for your height. This calculator supports both metric and imperial units and shows your BMI category instantly.

UnitsWeight

Height

Your BMI

22.9

CategoryNormal weight

Healthy range18.5 – 24.9

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How it works

BMI is your weight divided by your height squared. It is a simple screening measure used by health professionals to classify underweight, normal weight, overweight and obesity in adults.

BMI = weight (kg) ÷ height² (m²) — or 703 × weight (lb) ÷ height² (in²)

Worked examples

A 70 kg adult, 1.75 m tall (metric)
A 70 kg adult who is 1.75 m tall: 70 ÷ 1.75² = 70 ÷ 3.0625 = 22.9, which is in the normal-weight range.
A 154 lb adult, 69 in tall (imperial)
A 154 lb adult who is 69 in tall: 703 × 154 ÷ 69² = 22.7, also in the normal-weight range.
A reading that lands exactly on 25.0
An adult who weighs 81 kg and is 1.80 m tall has a BMI of 81 divided by 3.24 = 25.0, which sits exactly on the boundary between the normal and overweight bands used above. A single reading on a band edge is a classification question rather than a diagnosis, and a small change in either measurement can move the label.

What this assumes, and where it does not apply

What it assumes

Metric input is kilograms and metres, imperial is pounds and inches; the tool converts before applying the formula.
The published adult BMI categories are applied as they stand, to a result rounded to one decimal place.
The category is read from the value rounded to one decimal place, so a result just below or just above a boundary can fall either side of it once rounding is applied.

Where the result does not apply

Not valid for children or teenagers, who are assessed on age-specific BMI-for-age charts, nor for pregnant women.
BMI compares weight with height only. It cannot distinguish muscle from fat and says nothing about fitness or health.
A BMI worked out from a self-reported height or weight is only as good as those two figures, so it does not apply where either has been estimated rather than measured.

Frequently asked questions

What is a healthy BMI?

For most adults, a BMI between 18.5 and 24.9 is considered a healthy weight range.

What are the BMI categories?

Under 18.5 is underweight, 18.5–24.9 normal, 25–29.9 overweight, and 30 or above is obese.

Is BMI accurate for everyone?

BMI does not distinguish muscle from fat, so very muscular people may have a high BMI without excess body fat. It is a screening tool, not a diagnosis.

Is BMI different for children?

Yes. For children and teens, BMI is interpreted against age- and sex-specific percentiles rather than fixed cutoffs.

Does BMI tell me whether I am healthy?

No. BMI compares weight with height only. It cannot distinguish muscle from fat or show where fat is carried, so it is a screening measure that a clinician reads alongside other information, not a diagnosis.

This tool is for general information only and is not medical advice. Always consult a qualified healthcare professional before making health-related decisions.

Delta Tech Solutions prepared this page. No doctor, nurse or other qualified health professional reviewed it, and it is not medical advice — talk to a qualified healthcare professional about your own situation.

Sources: World Health Organization — obesity and overweight

Maintained by David M at Delta Tech Solutions · Figures last checked 10 October 2026 · Next check due 10 April 2027

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