BMI Calculator
Calculate adult body mass index and understand what the screening result can—and cannot—show.
Your BMI Result
Result status:
Practical interpretation
Important: Estimate only—not medical advice.
How the BMI Calculator works
Formula: BMI = weight (kg) ÷ height (m)².
The result is compared with standard adult screening thresholds: below 18.5, 18.5 to below 25, 25 to below 30, and 30 or above.
Assumptions and limits: BMI does not distinguish fat from muscle and adult cutoffs are not appropriate for children or pregnancy. Results are estimates for education and planning, not medical advice.
How to use your result
Use the result as a starting point, not a pass-or-fail score. Keep your inputs consistent, observe relevant trends over time, and adjust only when the trend—not one day—shows the estimate does not fit your needs.
Body measurements and equation-based targets always contain uncertainty. If your result conflicts with symptoms, a diagnosis, medication guidance, pregnancy needs, an eating-disorder recovery plan, or instructions from your care team, follow your qualified health professional.
Frequently Asked Questions
What does the BMI Calculator calculate?
It estimates calculate adult body mass index and its screening category. from the information you enter. It is a planning and screening estimate, not a diagnosis or individualized medical prescription.
Which formula does this BMI Calculator use?
This tool uses BMI = weight (kg) ÷ height (m)².. The formula and every adjustment are shown on this page so you can understand the assumptions.
Can I use metric or imperial units?
Yes. Choose metric or imperial before entering body measurements. Imperial values are converted to kilograms and centimeters before the formula runs.
How accurate is this BMI Calculator?
Population equations provide useful starting estimates but cannot measure your individual physiology. BMI does not distinguish fat from muscle and adult cutoffs are not appropriate for children or pregnancy.
Who should not rely on this result alone?
Children, pregnant or breastfeeding people, competitive athletes with specialized needs, and anyone managing a medical condition should seek advice from a qualified health professional.
How often should I recalculate?
Recalculate when your body weight, activity, goal, or other relevant input changes meaningfully. Small day-to-day fluctuations generally do not warrant a new target.
Why might my result differ from another calculator?
Calculators may use different equations, activity factors, rounding rules, or definitions. Compare the documented methods rather than assuming one number is exact.
Is this result medical advice?
No. This educational estimate cannot account for diagnoses, medications, laboratory results, or clinical fluid and nutrition restrictions. Consult a licensed professional for personal medical advice.
Scientific References
- Body mass index (BMI) World Health Organization
- Body Weight Planner and energy balance information National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
- ACSM Guidelines for Exercise Testing and Prescription American College of Sports Medicine