Adult BMI Calculator
Enter height and weight to calculate adult BMI. This English version defaults to US customary units (ft/in and lb), with cm/kg available as a secondary option. BMI is a screening estimate, not a medical diagnosis.
Inputs
Result
0.0kg/m²
Healthy weight
This adult BMI calculator is for screening and education. Children, teens, pregnancy, athletes, and people with unusual body composition may need a different assessment.
How should I read an adult BMI result?
BMI compares weight with height and is commonly used as a quick adult screening measure. This calculator keeps the input flow simple: choose the classification standard, choose units, enter height and weight, and review the BMI value with its category and healthy-weight range. It does not measure body fat directly and should not be used as a diagnosis.
How to use the calculator
Use CDC adult categories for a US-facing result. Use WHO adult classification when you want a broader international reference. The BMI formula is the same; the label wording differs slightly.
For this English page, the default is ft/in and lb, which is the representative US input style. Metric cm/kg remains available for users with metric measurements.
Use adult height and current weight. Decimal input is allowed. Values outside the adult calculator range show an error before calculation.
The result includes BMI, category, healthy-weight range for the entered height, distance from that range, formula, and the values used.
Which BMI standard is used?
Adult BMI thresholds are widely aligned around underweight below 18.5, healthy or normal weight from 18.5 to 24.9, overweight from 25.0 to 29.9, and obesity from 30.0 upward. CDC wording is most natural for a US English page, while WHO wording is useful when comparing with international material.
| Category | BMI | How to read it |
|---|---|---|
| Underweight | < 18.5 | May indicate weight below the adult reference range. |
| Healthy weight | 18.5–24.9 | The selected standard’s healthy range. |
| Overweight | 25.0–29.9 | Review with waist, activity, and health markers. |
| Class 1 obesity | 30.0–34.9 | One of the CDC adult obesity classes. |
| Class 2 obesity | 35.0–39.9 | A higher adult obesity class. |
| Class 3 obesity | ≥ 40.0 | Often called severe obesity in CDC materials. |
| Category | BMI | How to read it |
|---|---|---|
| Underweight | < 18.5 | Below the adult reference range. |
| Normal range | 18.5–24.9 | WHO normal adult range. |
| Overweight | 25.0–29.9 | WHO defines overweight as BMI 25 or higher. |
| Obesity class I | 30.0–34.9 | WHO obesity class I. |
| Obesity class II | 35.0–39.9 | WHO obesity class II. |
| Obesity class III | ≥ 40.0 | WHO obesity class III. |
Formula and examples
Metric formula
BMI = weight(kg) ÷ height(m)²
US customary formula
BMI = weight(lb) ÷ height(in)² × 703
The calculator converts units internally so both unit systems use the same BMI scale.
154 ÷ 67² × 703 = about 24.1. Under CDC adult categories, this is Healthy weight.
170 ÷ 67² × 703 = about 26.6. Under CDC adult categories, this is Overweight.
What the result means
A ratio of weight to height. It does not show body fat percentage, muscle mass, or fat distribution.
The weight range that matches the selected BMI standard for the entered height. It is not a personalized target weight.
A simple estimate of how far the entered weight is from the selected healthy range boundary.
When comparing results over time, use the same unit system, measurement conditions, and classification standard.
Input range and rounding
This adult calculator follows practical ranges used by adult BMI tools: 3–9 ft tall, 55–1,000 lb, or the metric equivalents 91.4–274.3 cm and 24.9–453.6 kg. Values outside those limits are likely entry mistakes or outside this tool’s intended use.
BMI, healthy-weight range, and difference values are rounded mainly to one decimal place for readability. US English output uses comma grouping and decimal points such as 1,000.0 lb.
Cautions
BMI is a screening measure, not a diagnosis. It may be less informative for children and teens, pregnancy, athletes, older adults, people with swelling, and people with body composition that differs from average adult reference groups. If the result is concerning, consider waist measurement, blood pressure, blood glucose, lipids, body composition, medical history, and professional guidance.
FAQ
Why does the English version default to ft/in and lb?
This page is localized as en-US for representative English-language use in the United States. Feet, inches, and pounds are the default, while cm/kg remains available for metric measurements.
Do I need to enter age or sex?
The adult BMI formula uses only height and weight. Children and teens need age- and sex-specific growth charts, so this adult calculator should not be used for them.
Is the healthy range my target weight?
No. It is a reference range from the selected BMI standard. A personal target depends on health status, history, habits, and professional advice.
Can athletes use BMI?
They can calculate it, but interpretation may be limited because BMI does not distinguish muscle from fat. Body composition and performance context matter.
Reference standards
CDC Adult BMI Calculator, CDC BMI formula guidance, and WHO Obesity and overweight fact sheet were used as references.