Calculators
BMI calculator
Enter weight in kilograms and height in centimetres to get the body mass index, the band it falls in and the weight range usually called healthy for that height.
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How it works
Body mass index is weight in kilograms divided by height in metres squared, so the height is converted from centimetres by dividing by one hundred before it is squared. A 70 kg adult at 1.75 m gives 70 ÷ 3.0625 = 22.86. The band comes from the adult cut-offs used by the World Health Organization: below 18.5 underweight, 18.5 to under 25 healthy, 25 to under 30 overweight, and 30 or above obese. The healthy weight range is the same formula rearranged, multiplying the squared height by 18.5 and by 24.9. The result is rounded to one decimal place. This is arithmetic, not a diagnosis.
Worked example
For 70 kg and 175 cm the height in metres is 1.75, and 1.75 squared is 3.0625. Dividing 70 by 3.0625 gives 22.86, which displays as 22.9 and falls in the healthy band. The healthy weight range for that height runs from 18.5 × 3.0625 = 56.7 kg to 24.9 × 3.0625 = 76.3 kg.
Questions and answers
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