1. The Calculation Is Simple
Adult BMI is calculated by dividing weight in kilograms by height in meters squared. For example, a height of 1.70 m and a weight of 65 kg gives a BMI of about 22.5. Accurately measuring height and weight under consistent conditions comes first. Adult categories should not be applied during pregnancy or to children and adolescents who are still growing.
2. Reading Adult Categories
The CDC’s adult categories are underweight below 18.5, healthy weight from 18.5 to below 25, overweight from 25 to below 30, and obesity at 30 or higher. Depending on the country and clinical guidelines, lower thresholds may also be used to assess health risks in Asian populations. Calculator categories are not diagnoses; they are a starting point for deciding whether further evaluation may be needed.
3. What BMI Misses
BMI cannot distinguish fat from muscle or show where fat is concentrated. People with a lot of muscle may have a higher BMI, and two people with the same BMI may differ in waist circumference and metabolic health. Age, medical history, and recent weight changes should also be considered.
4. Information to Check Alongside BMI
Checking waist circumference, blood pressure, blood sugar and blood lipid tests, medications, sleep, and activity levels can help you assess risk more accurately. Body fat percentages from home body-composition devices can also vary with hydration, so focus on trends measured under consistent conditions rather than a single number.
5. Choose Actions Instead of Chasing a Number
Rather than setting a goal of moving down one BMI category, choose measurable actions such as eating regular meals, spending more time walking, or doing strength training twice a week. Adults can gradually work toward 150 minutes of moderate-intensity aerobic activity and two days of strength training per week, as appropriate.
6. When to Seek Medical Advice
Seek medical care if you experience unintentional weight loss, rapid weight gain, dizziness, menstrual changes, or concerns about an eating disorder, regardless of your BMI. Children and adolescents should be assessed using growth charts based on age and sex, and adult calculator results should not be used.