Health calculator
BMI Calculator by Age and Sex
Calculate adult BMI from height and weight, then use age and sex for an estimated body-fat percentage and contextual guidance.
FormulaBMI = weight in kg / (height in meters)^2
Formula
BMI formula
BMI and BMI-based body-fat estimates are screening tools, not diagnoses. Children, teens, pregnancy, athletes, older adults, and people with unusual muscle mass may need different assessment.
BMI = weight in kg / (height in meters)^2
A person weighing 70 kg and 1.75 m tall has BMI = 70 / 1.75^2 = 22.86.
SourcesThis calculator includes source notes, assumptions, and exclusions so the result is easier to verify before use.
Sources and assumptions
Source notes
This calculator includes source notes, assumptions, and exclusions so the result is easier to verify before use.
- Effective year
- Current rules
- Last verified
- 2026-06-18
BMI and BMI-based body-fat estimates are screening tools, not diagnoses. Children, teens, pregnancy, athletes, older adults, and people with unusual muscle mass may need different assessment.
Official and reference sources
Assumptions
- Adult BMI categories are shown only for adults age 20 and older.
- Age and sex do not change the BMI formula or adult BMI category thresholds.
- Age and sex are used only for the optional BMI-based adult body-fat estimate.
Not included
- Child and teen BMI-for-age percentiles.
- Pregnancy-specific assessment.
- Direct body-composition measurement, diagnosis, or individualized clinical risk.
FAQ7 common questions for this calculator.
FAQs
What is a normal BMI range?+
For many adults, 18.5 to 24.9 is commonly classified as a normal BMI range.
Do age and sex change adult BMI?+
No. Adult BMI uses height and weight only. This calculator uses age and sex for a separate estimated body-fat percentage and for clearer interpretation notes.
Is BMI a medical diagnosis?+
No. BMI is a screening metric and should not replace professional medical advice.
How does the BMI Calculator calculate the result?+
For the BMI Calculator, it uses the BMI formula: BMI = weight in kg / (height in meters)^2. A person weighing 70 kg and 1.75 m tall has BMI = 70 / 1.75^2 = 22.86.
What information do I need to use the BMI Calculator?+
Enter height and weight, then choose metric or imperial units. Age and sex are used only for the companion body-fat estimate, while BMI itself uses height and weight.
How accurate is the BMI Calculator?+
BMI is accurate as a height-and-weight calculation, but it is only a screening measure. It does not directly measure fat, muscle, pregnancy status, age-specific child percentiles, or individual clinical risk.
What should I check before using the BMI Calculator result?+
Check height, weight, unit system, age, and sex before reading the result. Use adult BMI categories only for adults, and treat the body-fat estimate as a rough formula-based comparison.
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Health guide
How to use the BMI Calculator
Calculate adult BMI from height and weight, then use age and sex for an estimated body-fat percentage and contextual guidance. The page also explains the BMI formula and shows a practical example: A person weighing 70 kg and 1.75 m tall has BMI = 70 / 1.75^2 = 22.86.
- 1
Enter your details
Enter height and weight, then use age and sex, then complete any other fields shown in the calculator.
- 2
Check the calculation
Review the result alongside the BMI formula: BMI = weight in kg / (height in meters)^2.
- 3
Compare scenarios
Change one or more inputs to see how they affect the BMI Calculator result before you use the estimate.
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