BMI Calculator
Enter your height and weight in US or metric units. You get your BMI, your category and a healthy weight range.
By Muhammad AhmadUpdated October 2026Free, no sign-up
Results are estimates for planning and learning, not financial, tax or medical advice. Read our editorial policy.
How It Works
Body mass index (BMI) is a simple screening number that compares your weight to your height. This calculator accepts US units (feet, inches and pounds) or metric units (centimeters and kilograms), converts everything to a common standard, and shows your BMI, your weight category and the range of weights that would fall into the “healthy” BMI band for your height.
For adults, the Centers for Disease Control and Prevention uses these categories: below 18.5 is underweight, 18.5 to 24.9 is a healthy weight, 25.0 to 29.9 is overweight, and 30 or above is classified as obesity, with further classes at 35 and 40. The scale graphic shows where you land, and the “healthy weight range” shows the minimum and maximum weight for your height that produces a BMI between 18.5 and 24.9.
BMI is a quick and inexpensive screening tool, but it has well-known limits. It does not distinguish between muscle and fat, so athletes with high muscle mass can have a high BMI without excess body fat. It also does not account for age, sex, bone structure, or where fat is stored — waist circumference and body composition can add important context. Children and teens use age- and sex-specific BMI percentiles rather than these adult categories.
Use your result as a starting point for a conversation with a doctor, not a diagnosis. Combine it with other measures such as waist size, blood pressure, cholesterol, blood sugar, fitness level and family history. If you want to change your weight, small and sustainable changes in nutrition, activity and sleep tend to work better than extreme diets.
Formula Explained
US units: BMI = 703 × weight (lb) ÷ height (in)²
Metric units: BMI = weight (kg) ÷ height (m)²
Healthy weight range: weight = BMI × height² using BMI 18.5 and 24.9.
Frequently Asked Questions
What is a healthy BMI?
For adults, a BMI from 18.5 to 24.9 is considered a healthy weight range by the CDC.
Is BMI accurate for athletes?
Not always. BMI cannot distinguish muscle from fat, so muscular people may be classified as overweight despite low body fat.
Does BMI apply to children?
Children and teens use BMI-for-age percentiles that account for growth and sex, not the adult categories shown here.
How do I convert feet and inches to BMI?
Convert height to total inches, then use 703 × weight in pounds ÷ height in inches squared. The calculator does this automatically.
Is BMI the same for men and women?
The adult BMI formula and categories are the same, but body fat percentages differ between sexes at the same BMI.
What are better measures than BMI?
Waist circumference, body fat percentage, blood pressure, cholesterol and glucose give a fuller view of health risk.
How often should I check my BMI?
Occasionally is enough. Weight naturally fluctuates, so look at long-term trends rather than daily changes.
Should I see a doctor about my result?
If your BMI is outside the healthy range or you have health concerns, discuss it with a healthcare professional.