How to use the BMI calculator
- Choose metric or imperial.
- Enter your height and weight — your BMI and category update instantly.
BMI categories
- Under 18.5 — Underweight
- 18.5 – 24.9 — Healthy weight
- 25 – 29.9 — Overweight
- 30 and above — Obese
BMI is a general guide, not a diagnosis. It doesn't account for muscle mass or body composition. Talk to a doctor for personal health advice.
Benefits
- Calculates Body Mass Index in either metric or imperial units.
- Shows the standard weight category alongside the number.
- Runs privately in your browser.
- Free and instant.
Limitations to know
- BMI is a rough screening figure — it cannot tell muscle from fat and can misclassify athletes, older adults and different body types.
- It is not a medical diagnosis and does not replace advice from a health professional.
- It is not interpreted the same way for children, who need age-and-sex percentile charts.
Common mistakes to avoid
- Treating BMI as a precise verdict on your health.
- Mixing metric and imperial values in the two inputs.
- Applying an adult BMI category to a child.
Alternatives
For anything health-related, a doctor or registered dietitian can give context BMI cannot. For general percentage math, use the Percentage Calculator.
Last updated: August 2026 · Reviewed by the AI Toolbox editorial team.
Frequently asked questions
What is a healthy BMI?
For most adults, a BMI between 18.5 and 24.9 is considered healthy.
Is the BMI calculator free?
Yes, completely free with no sign-up.