Free BMI Calculator
Calculate your Body Mass Index using your height and weight. Choose metric or imperial units and get your BMI instantly.
What Is BMI?
Body Mass Index, commonly called BMI, is a numerical value calculated using a person's weight and height. It is commonly used as a general screening measure to classify weight ranges in adults.
BMI is calculated by dividing weight in kilograms by height in meters squared. This calculator supports both metric and imperial measurements.
How to Use the BMI Calculator
- Select Metric or Imperial units.
- Enter your height.
- Enter your weight.
- Click the Calculate BMI button.
- Review your BMI value and category.
Adult BMI Categories
For adults, BMI is commonly interpreted using the following general categories:
- Below 18.5 — Underweight
- 18.5 to 24.9 — Healthy weight
- 25.0 to 29.9 — Overweight
- 30.0 or above — Obesity
BMI Limitations
BMI is a screening measure rather than a complete assessment of individual health. It does not directly measure body fat and does not account for factors such as muscle mass, body composition, age, sex or distribution of body fat.
For this reason, BMI results should be interpreted as general information rather than a medical diagnosis. If you have questions about your weight or health, consider speaking with a qualified healthcare professional.
Frequently Asked Questions
Is the BMI Calculator free?
Yes. The ToolNest BMI Calculator is free to use and does not require an account.
What formula does the calculator use?
For metric measurements, BMI is calculated by dividing weight in kilograms by height in meters squared.
Can I use pounds and feet?
Yes. Select Imperial mode to enter height in feet and inches and weight in pounds.
Is BMI a medical diagnosis?
No. BMI is a general screening measurement and should not be treated as a diagnosis or complete assessment of health.
Can I use this calculator on mobile?
Yes. The calculator is responsive and works on smartphones, tablets and desktop devices.