Health / Body metrics

BMI Calculator

Calculate adult BMI, BMI prime, and the matching adult CDC comparison band from metric height and weight.

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Opening calculator...

How to use Use it in four checks

Enter height, weight and age using the units, labels, and choices shown on the form.

Check the assumptions so the result matches the situation you want to model.

Compare the result with the visible ranges, units, and assumptions on the page.

Use the breakdown table to see which inputs are driving the answer.

Formula steps How Bitneer gets the result

Start with height, weight and age; numeric entries must be valid before the calculator returns a result.

Apply the formula: BMI = weight kg / height m^2. BMI prime = BMI / 25.

Show bmi, bmi prime and adult bmi category in the result panel with the matching breakdown rows.

Round the display value while keeping the assumptions and example visible for review.

Formula How the formula works

B M I = \frac{W}{H ^{2}}

B M I_{p r im e} = \frac{B M I}{25}

BMI is a height-weight index. This worksheet uses the adult formula and shows the CDC adult comparison bands alongside BMI prime.

W: Weight Body weight in kilograms.
H: Height Height in meters.
BMI: Body mass index Weight divided by squared height.
BMI_{prime}: BMI prime BMI divided by 25.

Assumptions What this calculator assumes

Height is entered in centimeters and converted to meters.

Adult categories are for age 20 and older.

BMI does not account for muscle mass, body composition, pregnancy, or child growth percentiles.

Example

178 cm and 79 kg

178 cm and 79 kg returns 24.93 kg/m^2 with the current formula and default assumptions.

Expected result: 24.93 kg/m^2

Outputs What this calculator returns

BMI
BMI prime
Adult BMI category

FAQ Quick answers

What category bands are shown?

The adult comparison bands are underweight below 18.5, healthy weight from 18.5 to under 25, overweight from 25 to under 30, and obesity range at 30 or above.

What is BMI prime?

BMI prime divides BMI by 25, so 1.0 is the upper edge of the adult healthy-weight band.

Is this for children?

No. Children and teens need age-and-sex percentile charts rather than adult BMI bands.