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BMI Calculator (Body Mass Index)
Body mass index for adults from height and weight in pounds and feet or metric, with the CDC category and healthy weight range.
Calculated in your browser – nothing you enter is sent or stored.
Body mass index (BMI) compares your weight with your height. This BMI calculator works in pounds and feet/inches or kilograms and centimeters, shows your CDC weight category, and tells you the healthy weight range for your height – so you know not just the number but what it means for you. It is for adults aged 20 and over.
How to Use the BMI Calculator
- Choose US or metric units.
- Enter your height and weight – weigh yourself in the morning, without shoes, for the most consistent number.
- Enter your age. Under 20, BMI is judged against growth charts instead of the adult categories.
BMI Formula
- US units: BMI = 703 × weight (lb) ÷ height (in)²
- Metric: BMI = weight (kg) ÷ height (m)²
Example: someone 5 ft 9 in (69 inches) who weighs 170 lb has a BMI of 703 × 170 ÷ 69² = 119,510 ÷ 4,761 = 25.1, just inside the overweight range. A healthy BMI of 18.5–24.9 at that height means about 125 to 169 lb, so losing just over a pound would bring the BMI under 25.
Adult BMI Categories
| BMI | Category (CDC) |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Healthy weight |
| 25.0 – 29.9 | Overweight |
| 30.0 – 34.9 | Obesity class 1 |
| 35.0 – 39.9 | Obesity class 2 |
| 40.0 and above | Obesity class 3 (severe) |
The same categories apply to men and women. About 4 in 10 U.S. adults have a BMI of 30 or more, according to the CDC.
What BMI Doesn't Tell You
BMI is a quick screening tool, not a diagnosis. It doesn't measure body fat directly or show where fat is stored:
- Muscle: athletes and people who lift weights can have a BMI over 25 with little body fat.
- Age: older adults lose muscle, so a "normal" BMI can hide extra fat.
- Waist size: fat around the middle carries more health risk. A waist over 40 inches for men or 35 inches for women (not pregnant) is a warning sign at any BMI.
- Ethnicity: some groups, including people of Asian descent, face higher risk at lower BMIs.
Your doctor will look at BMI together with blood pressure, cholesterol, blood sugar and family history.
Next Steps
If your BMI is above the healthy range, the calorie deficit calculator shows how many calories to eat to reach a goal weight safely, and the TDEE calculator shows how many you burn now. For children and teens, use the CDC's child and teen BMI calculator, which compares BMI with others of the same age and sex.
Sources
- CDC – Adult BMI categories
- CDC – About body mass index (limitations)
- NIH National Heart, Lung, and Blood Institute – Assessing your weight and health risk
Last reviewed: October 2026 by the ShrinkBee team. BMI is a screening measure, not a diagnosis. This page is for education and is not medical advice.
Calorie Deficit Calculator TDEE Calculator Calorie Calculator BMR Calculator