Get a quick BMI (Body Mass Index) reading from your height and weight, plus what the number actually means.
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Body Mass Index (BMI) is a quick screening measure based on height and weight. It's not a full health assessment, but it's a useful starting reference point. This free calculator is built for adults and gives an instant result using the same formula and categories for both men and women.
How to Use
- Enter your height in feet and inches.
- Enter your weight in pounds.
- Click Calculate to see your BMI score and category.
Under the hood, this BMI calculator uses the standard US formula: weight in pounds, divided by height in inches squared, multiplied by 703.
This calculator uses US units (feet, inches, pounds). If you use kilograms and centimeters instead, divide your weight in kg by your height in meters squared to get the same BMI number.
Example: someone who is 5'6" and 110 lb has a BMI of 17.8 (Underweight). Someone who is 5'10" and 160 lb has a BMI of 23.0 (Normal). Someone who is 5'4" and 120 lb has a BMI of 20.6 (Normal). Someone who is 6'0" and 250 lb has a BMI of 33.9 (Obese). In metric terms, someone who is 175 cm and 70 kg also has a BMI of 22.9 (Normal), calculated as 70 divided by 1.75 squared.
BMI Categories
As a standard BMI calculator, this tool sorts your result into four widely used categories:
| BMI Range | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 - 24.9 | Normal weight |
| 25.0 - 29.9 | Overweight |
| 30.0 and above | Obese |
BMI does not account for muscle mass, bone density, or body composition. It's a general screening tool, not a diagnosis, and it isn't designed for children, pregnant women, or highly muscular athletes. Talk to a healthcare provider for a full picture of your health.
Did You Know?
The formula behind BMI is nearly 200 years old. Belgian mathematician and astronomer Adolphe Quetelet developed it in 1832 while studying population averages, and for well over a century it was known as the "Quetelet Index." Physiologist Ancel Keys popularized the modern name "Body Mass Index" in 1972 after researching it as a practical, low-cost way to screen large groups for weight-related health risk (source).
Frequently Asked Questions
What is a healthy BMI range?
For most adults, a BMI between 18.5 and 24.9 falls in the "normal weight" range used by major health organizations. Anything below that is considered underweight, and anything at or above 25 is considered overweight or obese. This same formula and the same category cutoffs are used for both men and women; BMI itself does not adjust for sex.
What is the BMI formula?
In US units, BMI equals weight in pounds divided by height in inches squared, multiplied by 703. In metric units, it's simply weight in kilograms divided by height in meters squared.
Is BMI accurate for athletes or very muscular people?
Not reliably. Muscle is denser than fat, so a muscular, low-body-fat athlete can score in the "overweight" or "obese" range on BMI alone even though their actual body fat percentage is low. BMI can't tell the difference between muscle and fat, it only looks at total weight relative to height.
Does BMI work the same way for children and teens?
No. Kids and teens are still growing, so pediatric BMI is plotted on age- and sex-specific growth charts as a percentile, such as the CDC or WHO growth charts, rather than compared against the fixed adult categories used here. This calculator is intended for adults; a pediatrician is the right resource for interpreting a child's growth chart.
What are the main limitations of BMI as a health measure?
BMI is a fast screening number, not a diagnosis. It doesn't measure body fat percentage, muscle mass, bone density, or where fat is distributed on the body, and it doesn't adjust for age, sex, or ethnicity, all of which can affect what a healthy weight looks like for a given person. It's best used as a starting point alongside other measurements and a conversation with a healthcare provider, not as a standalone verdict.
Related Tools
The Unit Converter is handy if you have your height or weight in metric and want to convert it to feet/inches or pounds first. The Percentage Calculator is useful for tracking a percentage change in body weight over time, and the Age Calculator can help if you're looking up age-based health reference ranges.