BMI calculator (body mass index) from weight and height
Enter the weight in kilograms and the height in centimetres. You get the body mass index (BMI) in kg/m², to one decimal place, and the height in metres squared.
For: Any age: it asks only for weight and height and returns the figure, without classifying it. Free, no sign-up. Everything is worked out in your browser and nothing is stored.
How BMI is worked out
The body mass index relates weight to height. It is calculated by dividing the weight in kilograms by the height in metres squared:
BMI = weight (kg) / height (m)²
Because the calculator asks for the height in centimetres, it first converts it to metres: 175 cm is 1.75 m and 1.75² = 3.0625. The result is given in kg/m² to one decimal place; it is rounded to two decimals first, so 22.449 is shown as 22.5.
| Weight | Height | Height² | BMI |
|---|---|---|---|
| 3,2 kg | 50 cm | 0,2500 m² | 12,8 kg/m² |
| 18 kg | 110 cm | 1,2100 m² | 14,9 kg/m² |
| 55 kg | 160 cm | 2,5600 m² | 21,5 kg/m² |
| 70 kg | 175 cm | 3,0625 m² | 22,9 kg/m² |
| 95 kg | 180 cm | 3,2400 m² | 29,3 kg/m² |
How to read the result
This calculator returns the BMI value but does not classify it: it asks for neither age nor sex. The same BMI means different things at different ages.
- For children and adolescents aged 5 to 18, BMI is assessed by age and sex using the z-score from the Chilean Ministry of Health growth standards (2018). That is what the BMI z-score calculator.
- For adults it is compared with the cut-off points of the technical standard in force for their age group.
BMI is a supporting indicator: a nutritional diagnosis also takes in the person's history, the clinical examination and other measurements.
Frequently asked questions
How is BMI calculated?
Weight in kilograms is divided by height in metres squared. For example, 70 kg and 175 cm: 1.75 × 1.75 = 3.0625 and 70 / 3.0625 = 22.9 kg/m².
What units should I use for weight and height?
Weight in kilograms and height in centimetres. You can use a comma or a full stop as the decimal mark. If you enter the height in metres (1.75 instead of 175), the result comes out thousands of times too high: the calculator does not catch that.
Does the calculator say whether the BMI is normal?
No. It returns only the BMI value. Interpretation depends on age: for children and adolescents aged 5 to 18 the BMI-for-age-and-sex z-score is used, and for adults the cut-off points of the technical standard in force.
How many decimal places does the result have?
One. The BMI is first rounded to two decimal places and that value is rounded to one: 22.449 becomes 22.45 and is shown as 22.5.
Is the data I enter stored?
No. Everything is worked out in your browser; no data is sent or stored.
Source
Patrones de crecimiento para la evaluación nutricional de niños, niñas y adolescentes, desde el nacimiento hasta los 19 años de edad (Growth standards for the nutritional assessment of children and adolescents from birth to 19 years). Ministerio de Salud, Chile, 2018.
A support tool for health professionals. It does not replace clinical assessment or the technical standard in force.