BMI Calculator
Calculate adult body mass index in pounds/feet or kilograms/centimeters.
About this bmi calculator
Body mass index (BMI) is a simple screening number that compares weight to height. Doctors and public-health agencies such as the CDC and WHO use it to sort adults into broad weight categories, because it's quick, free and correlates with health risk across large populations.
BMI has real limits for individuals: it can't tell muscle from fat, doesn't show where fat is carried, and its standard cut-offs don't fit everyone equally. Treat the result as a starting point for a conversation with your doctor, not a diagnosis. This calculator is for adults 20 and older; children and teens use age- and sex-specific percentiles instead.
How to use the BMI Calculator
- Choose US or metric units.
- Enter your weight and height.
- Read your BMI, its category and the healthy weight range for your height.
The BMI formula and categories
BMI = weight (kg) ÷ height (m)² · BMI = 703 × weight (lb) ÷ height (in)²
Adult categories used by the CDC: under 18.5 underweight, 18.5–24.9 healthy weight, 25–29.9 overweight, and 30 or higher obesity. The healthy weight range shown is the weight that gives a BMI of 18.5–24.9 at your height.
Worked example
A person who is 5 ft 9 in (69 inches) and weighs 170 lb has a BMI of 703 × 170 ÷ 69² ≈ 25.1, just inside the overweight category. Their healthy weight range is about 125–169 lb.
| BMI | Adult category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Healthy weight |
| 25.0 – 29.9 | Overweight |
| 30.0 and above | Obesity |
Tips for better results
- Measure height without shoes and weigh yourself at the same time of day for consistency.
- Waist circumference adds useful information that BMI misses.
Frequently asked questions
Is BMI accurate for athletes?
Often not. Muscular people can have a high BMI with low body fat, so BMI may overstate their risk.
Can children use this BMI calculator?
No. For ages 2–19, BMI is compared to growth charts by age and sex. Ask a pediatrician or use the CDC's child and teen BMI tool.
What is a healthy BMI?
For most adults, 18.5 to 24.9 is considered the healthy range.
This tool gives a general estimate and is not medical advice. Talk to a doctor or registered dietitian about your individual needs.
Last reviewed: October 2026 · Results are calculated in your browser.