BMI Calculator – Calculate Your Body Mass Index
Calculate your Body Mass Index from height and weight and see which category you are in.
About the BMI Calculator
What is the BMI Calculator?
A BMI calculator estimates body fat indirectly from your height and weight using the Body Mass Index.
Why use this calculator?
BMI is the most common first screening tool for weight-related health risk. It is quick, free and its categories align well with population-level risk studies.
How to use it
- Choose Metric or US units.
- Enter your weight and height.
- Read your BMI value and category.
- Compare your weight with the healthy range shown.
Formula
BMI = weight (kg) ÷ height (m)\u00b2
BMI does not measure body fat directly and can misclassify very muscular people or older adults. Use it as a starting point, not a diagnosis.
Frequently Asked Questions
Is BMI accurate for athletes?
Often not. Muscle is dense, so muscular people can show a high BMI while having low body fat. Use body-fat measurement too in that case.
Why does BMI use kg/m\u00b2?
That formula, developed by Adolphe Quetelet in the 1800s, normalizes weight by height so the score is comparable across different heights.
Can BMI be different for children?
Yes. For children, BMI is compared with age-specific percentiles rather than adult cut-offs.
Is this a medical diagnosis?
No. This tool provides general wellness information only. It is not a substitute for evaluation by a qualified healthcare professional.
Why do results differ from my doctor's measurements?
Clinical measurements use calibrated equipment and professional technique. Home estimates rely on formulas and self-reported values, so small differences are normal.
How often should I recalculate?
Recheck after meaningful changes such as weight gain or loss, a new workout routine, or every few months to track trends over time.
Do these formulas apply to everyone?
Most population formulas are less accurate for athletes, pregnant people, very young children and the elderly. Use them as a general guide.
Is this calculator free to use?
Yes. Every calculator on this site is completely free, with no hidden fees, no subscriptions and no limits on how many times you can use it.
How accurate are the results?
We use standard, widely accepted formulas and calculate in your browser using double-precision arithmetic. Results are rounded for readability, so treat them as reliable estimates rather than a guarantee. Real-world factors can vary the true figure.
Can I add this calculator to my own website?
Yes. Open this calculator page and use the "Add to your website" box in the sidebar to copy a ready-made iframe snippet, then paste it into any HTML page.