BMI Calculator
Calculate adult BMI from metric or imperial height and weight. See the BMI value, adult screening category, and formula for ages 20 and above.
For adults aged 20 and older. BMI is a screening measure, not a diagnosis; it does not distinguish muscle from fat or assess your overall health.
Adult BMI result
Enter your age, weight, and height to calculate adult BMI.
BMI = weight in kilograms ÷ (height in meters)². Pounds are converted using 1 lb = exactly 0.45359237 kg.
Adult categories: underweight below 18.5; healthy weight 18.5–<25; overweight 25–<30; class 1 obesity 30–<35; class 2 obesity 35–<40; class 3 obesity 40 or above.
CDC adult BMI categories. A health professional can interpret BMI alongside other health information.
How to use BMI Calculator
- Confirm an age of 20 or above and choose metric or imperial measurements.
- Enter height and weight using the labeled units.
- Calculate to see BMI and its adult screening category.
What is BMI Calculator?
Body mass index is weight in kilograms divided by height in meters squared. Adult categories group this ratio into ranges; they do not measure body composition or determine an individual's health. This calculator uses the CDC adult categories for people aged 20 and older and does not calculate child or teen percentiles.
- Metric and imperial inputs
- Adult category based on the unrounded BMI
- Clear formula and screening context
- No storage or upload of height, weight, or age
Interpreting the category
Adult thresholds are below 18.5, 18.5 to below 25, 25 to below 30, and 30 or above. The last category is further divided at 35 and 40. The tool presents these ranges without prescribing a target weight, diet, or medical treatment.
A practical example
Age 30 · 70 kg · 175 cm
BMI 22.9 Healthy weight range
Frequently asked questions
Who can use these BMI categories?
The categories shown are for adults aged 20 and older. Children and teens require age- and sex-specific percentile calculations, which this tool does not provide.
Is the category calculated from the rounded result?
No. Categories use the underlying BMI before display rounding, avoiding changes caused by rounding at a boundary.
Does BMI diagnose a health condition?
No. BMI is a screening measure to consider with other information. It does not assess muscle mass, pregnancy, or an individual's complete health.