Your BMI, in context.
A simple adult screening tool. A clearer explanation.
Your BMI
Add your height and weight to begin.
- Severe Thinness< 16
- Moderate Thinness16 – < 17
- Mild Thinness17 – < 18.5
- Normal18.5 – < 25
- Overweight25 – < 30
- Obese Class I30 – < 35
- Obese Class II35 – < 40
- Obese Class III≥ 40
BMI is one screening measure, not a diagnosis or a weight goal. It does not distinguish muscle from fat and is not suitable for pregnancy.
How we calculate
BMI Calc Now
AI assistant · Calculate BMI
Ask general questions about BMI methods, units or limitations. Do not share personal measurements or health details.
How to Use This Calculator
Choose your unit system
Toggle between Metric (kg/cm) and Imperial (lbs/ft-in). All labels update automatically.
Enter your weight
Enter your weight in kilograms for metric units or pounds for imperial units.
Enter your height
Enter your height in centimeters for metric units. For imperial units, enter feet and inches in their separate fields.
View your results
With valid height and weight, your BMI updates automatically. Review the category, visual scale, reference weight range, BMI Prime, and Ponderal Index. The reference range is not a personal weight goal.
Copy or share your result
Click the copy button to save your BMI result to your clipboard. Share it with your healthcare provider or keep it for your personal records.
A reproducible calculation
Body mass index (BMI) is weight in kilograms divided by height in metres squared. It is one screening measure, not a diagnosis or a direct measurement of body fat.
Imperial inputs are converted using 1 lb = 0.45359237 kg and 1 in = 2.54 cm. Five feet nine inches is 69 inches, not 5.9 feet.
- Weight
- 150 lb = 68.0388555 kg
- Height
- 5 ft 9 in = 175.26 cm
- Your BMI
- 22.1509004 → 22.2 kg/m²
Units are converted before calculation. Categories use the unrounded result; only the display is rounded. The shortcut multiplier 703 can differ slightly from exact conversion.
Adult (20+), not pregnant. For ages 2–19, use a validated BMI-for-age calculator. This tool shows adult ranges only. BMI is one screening measure, not a diagnosis or a weight goal. It does not distinguish muscle from fat and is not suitable for pregnancy.
The standard adult BMI formula is the same for women and men. The same BMI does not establish the same body composition or personal health risk.
This explanation checks the method and arithmetic. It does not claim an independent medical review. Personal interpretation requires context and an appropriate healthcare professional.
Sources below are in English.
What Is BMI?
Body mass index (BMI) is weight in kilograms divided by height in metres squared. It is one screening measure, not a diagnosis or a direct measurement of body fat. Imperial inputs are converted using 1 lb = 0.45359237 kg and 1 in = 2.54 cm. Five feet nine inches is 69 inches, not 5.9 feet. BMI is one screening measure, not a diagnosis or a weight goal. It does not distinguish muscle from fat and is not suitable for pregnancy.
BMI = kg / m²
BMI Classification Table (WHO)
Screening scope
How we calculate
Body mass index (BMI) is weight in kilograms divided by height in metres squared. It is one screening measure, not a diagnosis or a direct measurement of body fat.
- Imperial inputs are converted using 1 lb = 0.45359237 kg and 1 in = 2.54 cm. Five feet nine inches is 69 inches, not 5.9 feet.
- Units are converted before calculation. Categories use the unrounded result; only the display is rounded. The shortcut multiplier 703 can differ slightly from exact conversion.
Limitations of BMI
Research about groups cannot turn height and weight into an individual's disease probability or life expectancy. A BMI category is not a diagnosis or a treatment decision. Consider a study's population, comparison and limitations before applying a finding to a person.
- Adult (20+), not pregnant
- For ages 2–19, use a validated BMI-for-age calculator. This tool shows adult ranges only.
- BMI is one screening measure, not a diagnosis or a weight goal. It does not distinguish muscle from fat and is not suitable for pregnancy.
- The standard adult BMI formula is the same for women and men. The same BMI does not establish the same body composition or personal health risk.
This explanation checks the method and arithmetic. It does not claim an independent medical review. Personal interpretation requires context and an appropriate healthcare professional.
Limitations of BMI
BMI is one screening measure, not a diagnosis or a weight goal. It does not distinguish muscle from fat and is not suitable for pregnancy.
Frequently Asked Questions
Related Guides & Tools
Understanding BMI: A Complete Guide
Body mass index (BMI) is weight in kilograms divided by height in metres squared. It is one screening measure, not a diagnosis or a direct measurement of body fat.
BMI vs Body Fat Percentage: What's the Difference?
BMI and body fat percentage answer different questions. BMI uses height and weight; it cannot identify how much weight is muscle, fat or bone. Body-composition measurements and estimates have their own methods and uncertainty. A BMI value cannot confirm fitness or be converted into a reliable body-fat percentage on its own.
Practical checks before interpreting BMI
Check the units, how height was entered, the formula and the rounding convention before comparing results. A change in a displayed number is not by itself a change in health. Keep the calculation separate from personal treatment or weight goals.
Adult BMI by age: reference ranges and limits
For adults aged 20 and older, the standard BMI calculation does not add an age correction. Reference categories alone do not establish an ideal BMI for a particular age. Older adults may need additional clinical context, including muscle and health history; this tool does not supply that assessment. Children and teenagers require a separate age-specific method.
BMI and pregnancy: why the adult chart has limits
This tool does not interpret pregnancy measurements. Pre-pregnancy BMI can be one input used by a healthcare provider, while pregnancy weight includes changes that an ordinary adult chart does not interpret. Do not use a current adult category as a pregnancy weight-loss target. CDC's US pregnancy guidance separates recommendations by pre-pregnancy context and number of babies; a personal plan belongs with the pregnancy care team.
BMI calculator for adult women: formula and limits
The standard adult BMI formula is the same for women and men. The same BMI does not establish the same body composition or personal health risk.
BMI and health risk: interpreting a screening measure
Research about groups cannot turn height and weight into an individual's disease probability or life expectancy. A BMI category is not a diagnosis or a treatment decision. Consider a study's population, comparison and limitations before applying a finding to a person.
Lowering BMI: what the calculation can explain
At a fixed height, a lower weight produces a lower BMI mathematically. This does not establish whether weight loss is appropriate for an individual, how it should be achieved, or a safe timetable. Recheck consistent measurements and discuss personal interpretation with an appropriate healthcare professional. This calculator does not prescribe diets, exercise or treatment.
How the BMI Formula Works — A Step-by-Step Calculation
BMI = kg / m²
Imperial inputs are converted using 1 lb = 0.45359237 kg and 1 in = 2.54 cm. Five feet nine inches is 69 inches, not 5.9 feet. Units are converted before calculation. Categories use the unrounded result; only the display is rounded. The shortcut multiplier 703 can differ slightly from exact conversion.
A reproducible calculation: Metric (kg/cm)
- Step 1: 1.7526 m × 1.7526 m = 3.07160676 m²
- Step 2: 68.0388555 kg / 3.07160676 m² ≈ 22.1509004 kg/m²
- Step 3: Normal: 18.5 ≤ BMI < 25
- Step 4: BMI Prime = BMI / 25 ≈ 0.886036
A reproducible calculation: Imperial (lbs/ft-in)
- Step 1: 150 lb × 0.45359237 kg/lb = 68.0388555 kg
- Step 2: 5 ft 9 in = 69 in = 175.26 cm = 1.7526 m
- Step 3: BMI ≈ 22.1509004 → 22.2 kg/m²
- Step 4: Units are converted before calculation. Categories use the unrounded result; only the display is rounded. The shortcut multiplier 703 can differ slightly from exact conversion.