Which classification standard is used?
All languages use US CDC categories for adults aged 20 or older. For example, BMI 27 is Overweight. Classification uses the unrounded BMI.
BODY MASS INDEX
BMI Calculator & Weight from BMI
Calculate BMI from height and weight, or calculate weight for any BMI. Classification uses US CDC categories for adults aged 20 or older.
All calculations run in your browser. Height, weight and BMI are not sent to the server or saved.
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Calculate BMI
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Calculate weight from BMI
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Enter positive decimal numbers up to 1,000,000, with at most 32 characters. Use a decimal point; exponents and commas are not accepted. These are calculation limits, not recommended body measurements.
BMI classification standards
CDC adult categories are for people aged 20 or older, with the same thresholds for women and men. Do not apply them to children or adolescents.
| BMI range | Category |
|---|---|
| < 18.5 | Underweight — Current result |
| 18.5 ≤ BMI < 25 | Healthy Weight — Current result |
| 25 ≤ BMI < 30 | Overweight — Current result |
| 30 ≤ BMI < 35 | Class 1 Obesity — Current result |
| 35 ≤ BMI < 40 | Class 2 Obesity — Current result |
| 40 ≤ BMI | Class 3 Obesity — Current result |
Sources
What is BMI?
BMI (Body Mass Index) expresses weight relative to height. It is a screening measure for adults, not a diagnosis of health or a direct measurement of body fat.
How to calculate BMI
BMI = weight (kg) ÷ [height (m) × height (m)]. At 170 cm and 65 kg: 65 ÷ (1.7 × 1.7) ≈ 22.5.
How to calculate weight from BMI
Weight (kg) = specified BMI × [height (m) × height (m)]. At 170 cm and BMI 22: 22 × (1.7 × 1.7) ≈ 63.6 kg. This is a mathematical reference, not a personal target weight.
Things to keep in mind
BMI cannot distinguish muscle from fat, so it has limitations for people with high muscle mass. It does not show fat distribution or overall health. Older adults also need attention to undernutrition. General adult categories should not be applied during pregnancy or growth. BMI 22 is not a value everyone should aim for. Results are reference values and do not provide medical judgments or weight-loss instructions.
Frequently asked questions
Is BMI 22 an ideal weight for everyone?
No. Appropriate weight depends on individual circumstances; this calculator does not set a weight goal.
Can I use the adult classification for a child?
No. Children and adolescents need an assessment that accounts for age and growth. CDC adult categories apply from age 20.