Health
BMI Calculator
Calculate an adult BMI screening estimate from height and weight. Categories apply to ages 20 and older; not a diagnosis.
Guide
How to use the BMI Calculator
The BMI Calculator helps you make a quick estimate, compare scenarios, and understand the numbers behind the result. It is designed for fast planning, with enough context to make the answer useful instead of just a number.
- Enter current measurements as accurately as possible, using the unit system that fits you best.
- Read the equation, reference assumptions and limitations alongside the estimate.
- Adjust assumptions such as activity level, sex, age, or goal where the calculator supports them.
Method
How this calculator works
BMI = kilograms / meters squared. The displayed adult categories apply to ages 20 and older, not children's age-specific percentiles.
This calculator is useful for an adult body-size screening illustration, not a diagnosis or body-fat measurement.
Because assumptions matter, try a few values that represent optimistic, typical, and conservative cases.
Health calculators are screening and planning tools, not medical advice. They cannot replace a clinician's evaluation.
Example
Worked example
At 170 cm and 70 kg, BMI = 70 / 1.7 squared = 24.2 after rounding. Classification uses the unrounded value: a displayed 25.0 can be near a boundary.
FAQ
Common questions
What is a healthy adult BMI category?
CDC's adult screening category is BMI 18.5 to below 25 for ages 20 and older. BMI alone does not determine health or distinguish muscle from fat.
Can this calculate a child's BMI percentile?
No. This tool uses adult cutoffs, not age- and sex-specific growth charts. Use a pediatric assessment for children and teens.
What information do I need for the BMI?
You usually need positive height and weight in metric or imperial units. You can change the inputs and recalculate as many times as needed.
How does the BMI calculate the result?
BMI = kilograms / meters squared. The displayed adult categories apply to ages 20 and older, not children's age-specific percentiles.
Are the results exact?
Health calculators are screening and planning tools, not medical advice. They cannot replace a clinician's evaluation.
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