BMI calculator
Calculate body mass index from height and weight.
Fill in the fields and the result will appear here automatically.
BMI relates body mass to height squared and assigns an adult screening category. These categories are for people aged 20 and over. BMI does not distinguish muscle from fat or describe fat distribution. The displayed weight interval reverses the category 18.5 ≤ BMI < 25; it is not an individual weight target.
How it works
Formula and logic
BMI = weight in kg / (height in cm / 100)². The healthy category includes 18.5 and excludes 25; subsequent boundaries are 30, 35 and 40. For height h in metres, the corresponding lower weight is 18.5h² and the excluded upper boundary is 25h².
Example
At 175 cm and 70 kg, BMI = 70 / 1.75² = 22.857… → 22.9, in the healthy category. At 200 cm and 99.99 kg, 24.9975 displays as 25.0 but remains below the category boundary of 25.
Fields and units
- Height — cm
- Weight — kg
How to use
- — Enter measured height in centimetres and weight in kilograms, both positive.
- — Use these adult categories from age 20; this form does not check age.
- — Read the category before making an interpretation: it uses BMI before rounding.
- — Near a boundary, allow for the one-decimal display.
Method and limitations
- Calculation method
- Formula and logic
- Data or methodology source
- CDC: adult BMI categories from age 20 and unrounded cut-offs
- Limitation
- Adult screening information, not a diagnosis or individual weight goal. Pregnancy, muscular build and changes in body composition need additional context.
FAQ
What is the adult healthy BMI interval?
18.5 ≤ BMI < 25. The shorthand 18.5–24.9 does not describe every value between tenths.
Why can an athlete have a high BMI?
Muscle mass contributes to weight just as fat does. BMI alone cannot identify a body-fat percentage.
What health information does BMI miss?
It does not describe fat distribution, body composition or medical circumstances. Equal BMI values do not imply equal health.
Can children and teenagers use these categories?
No. Ages 2–19 require interpretation by age and sex rather than these adult cut-offs.
How should I interpret a high BMI or the weight interval?
Check measurements and units first. Consider the category alongside other information; the reverse-calculated weight interval does not prescribe weight loss or gain.