Adult BMI Calculator — US & Metric
Calculate body mass index using pounds and feet/inches or kilograms and centimeters. See the standard adult BMI category, a reference weight interval, and a visual comparison. Free, private, and no account required.
Calculate your BMI
Where your BMI falls
The spectrum is illustrative, not a medical risk scale. Its display spans BMI 12–45.
Weight reference comparison
Compare your current weight with weights corresponding to several BMI reference points at the same height. These are mathematical reference points, not personalized goals.
Bars rescale to fit the largest shown value.
Calculation shown
How BMI is calculated
BMI equals weight in kilograms divided by height in meters squared. For US measurements, the calculator converts pounds to kilograms and inches to meters before calculating. The result is rounded to one decimal place for display.
For example, a person who weighs 80 kg and is 1.80 m tall has a BMI of approximately 24.7 (80 ÷ 1.80²). This calculation describes a weight-to-height ratio, not a direct body-fat percentage.
Standard adult BMI categories
| Category | BMI | Interpretation |
|---|---|---|
| Underweight | Below 18.5 | Below standard adult reference range |
| Healthy weight | 18.5–24.9 | Within standard adult reference range |
| Overweight | 25.0–29.9 | Above standard adult reference range |
| Obesity | 30.0 or higher | Additional clinical context is important |
These are standard adult screening categories, not a diagnosis. Age, muscle mass, body composition, pregnancy, and other factors can affect interpretation.
Why use this BMI tool?
You can switch between US and metric measurements, instantly see the BMI category, inspect the mathematical weight interval corresponding to BMI 18.5–24.9, and compare reference points visually. All calculations happen in your browser; the tool does not require an account or ask for a name.
For interpretation details, read our in-depth BMI guide, worked examples, and methodology and assumptions.
Important limitations
BMI cannot distinguish fat from muscle or account for where fat is distributed. An athletic person may have a higher BMI without excess body fat. People with certain health conditions may need different assessments. BMI-for-age measures are used for children and teens; this calculator is not intended for them.
Do not use the mathematical weight range as an instruction to change weight. For personalized health questions, consult a qualified health professional.