DIY Cost Tools
Adult BMI Calculator
Health Screening Calculator
Adult BMI Calculator
Calculate adult body mass index using U.S. or metric measurements and review the CDC screening category and important limitations.
Calculate adult BMI
How to use the adult BMI calculator
Choose U.S. customary or metric units, then enter height and weight. The calculator reports BMI, the corresponding CDC adult category, and the weight range at that height that produces a BMI from 18.5 through 24.9.
BMI formulas
BMI = weight in kilograms / height in meters squared
For U.S. measurements, pounds are converted to kilograms and total inches are converted to meters before the same metric formula is used. The category thresholds follow current CDC adult ranges.
Worked example
An adult who is 5 feet 8 inches tall and weighs 165 pounds has a BMI of about 25.1. Under CDC adult thresholds, that falls in the overweight category. The result is a screening signal only and does not establish an individual's health status.
Important limitations
The CDC describes BMI as a screening measure that should be considered with other factors. It does not directly measure body composition and can be less informative for people with high muscularity, pregnancy, older age, or other individual circumstances. Children and teens require age- and sex-specific BMI percentiles and should not use this adult calculator.
Adult BMI categories
- Underweight: below 18.5
- Healthy weight: 18.5 to 24.9
- Overweight: 25.0 to 29.9
- Obesity class 1: 30.0 to 34.9
- Obesity class 2: 35.0 to 39.9
- Obesity class 3: 40.0 or greater
Frequently asked questions
Is BMI a diagnosis?
No. BMI is a screening measure. A clinician can interpret it alongside medical history, measurements, laboratory results, medications, and other relevant information.
Can children use this calculator?
No. The CDC uses BMI-for-age percentiles for people ages 2 through 19. This page is for adults 20 and older.
Why does the weight range not prove a healthy weight?
It only translates the standard BMI interval for the entered height. Individual health cannot be reduced to BMI alone.
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Sources and review
Formulas and adult thresholds follow the U.S. Centers for Disease Control and Prevention resources on calculating BMI and adult BMI categories. Calculator logic and examples were reviewed by the DIY Cost Tools editorial team on September 28, 2026.
Health notice: This educational calculator does not provide medical advice, diagnosis, or treatment. Discuss health concerns with a qualified healthcare professional.