Health calculator
BMI Calculator
Calculate adult BMI from height and weight, then use age and sex for an estimated body-fat percentage and contextual guidance.
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.
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.
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?+
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?+
Calculate adult BMI from height and weight, then use age and sex for an estimated body-fat percentage and contextual guidance.
How accurate is the BMI Calculator?+
BMI Calculator applies the formula and assumptions shown on this page. Results may be rounded for readability, so verify changing rates, thresholds, medical guidance, or legal rules with the cited source or a qualified professional.
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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