Metric formula
BMI = weight (kg) ÷ height (m)²
Measure height in metres, square it, then divide weight in kilograms by that number.
Free health tool
BMI Calculator
For adult women and men, enter your height and weight in pounds and inches or kg and cm to calculate your Body Mass Index, see your WHO category, and understand what the result can—and cannot—tell you.
Calculate your BMI
Start with pounds and inches, or switch to metric at any time.
Please enter a height from 80–250 cm and a weight from 20–350 kg.
Please enter a height from 2 ft 7 in–8 ft 2 in and a weight from 44–772 lb.
Your BMI
25.0
kg/m²
Category
Overweight
Healthy weight for your height
55–74 kg
About the result
What this BMI calculator does
BMI compares your weight with your height. Enter pounds and inches—or switch to kilograms and centimetres—and this calculator gives you an instant result, the standard adult WHO category, a healthy-weight range for your height, and a visual indicator showing where the number sits.
It is designed for adults. Children and teenagers need BMI-for-age percentiles that account for age and sex.
The calculation
How to calculate BMI
Imperial formula
BMI = 703 × weight (lb) ÷ height (in)²
This is the BMI formula using inches and pounds: convert total height to inches, square it, then divide 703 times the weight by that number.
Adult BMI chart
BMI chart for adults
This adult BMI chart uses standard WHO categories. It is the same scale used in the calculator above and applies to adults, regardless of sex.
Below 18.5UnderweightBelow the standard healthy range
18.5–24.9Healthy weightStandard healthy range for most adults
25.0–29.9OverweightAbove the standard healthy range
30.0 and aboveObesity rangeConsider the result with a healthcare professional
Worked example
Follow the formula step by step
1Convert your height from centimetres to metres.
2Square your height in metres.
3Divide your weight in kilograms by that figure.
BMI limitations
BMI limitations: why it is useful—and where it falls short
The limitations of BMI matter when a number is treated as a full picture of health. Use it as a starting point, then consider body composition, measurements, health history, and changes over time.
Useful as a quick screening measure
BMI is inexpensive, easy to calculate, and useful for identifying weight ranges that may be associated with higher health risk across populations.
Not a measure of body composition
BMI cannot distinguish muscle from body fat or show where fat is stored. It can overestimate risk in muscular people and miss risk in people with lower muscle mass.
Better measurements
Common mistakes to avoid
- Measuring in shoes. Measure height barefoot and stand upright against a flat wall.
- Comparing different times of day. Body weight naturally changes; use similar conditions when tracking a trend.
- Focusing on one decimal. Small differences around a category boundary are not meaningful on their own.
- Using adult cutoffs for children. Anyone under 20 should use an appropriate BMI-for-age assessment.
Your next step
What to do with your result
Look at the result as one part of a wider health picture. Waist measurement, blood pressure, laboratory results, activity, nutrition, sleep, medical history, and changes over time can all add context.
Common questions
Frequently asked questions
What is BMI?
BMI means Body Mass Index. It is a screening calculation that compares weight with height and helps place most adults into standard BMI categories.
What are the limitations of BMI?
BMI cannot distinguish muscle from body fat, show where fat is stored, or account for an individual’s health history. It is a useful screening measure, not a diagnosis.
What is a healthy BMI for an adult?
For most adults, the standard healthy BMI range is 18.5 to 24.9. BMI is a screening measure, so the number should be considered alongside other health information.
How is BMI calculated?
In metric units, divide weight in kilograms by height in metres squared. In imperial units, multiply weight in pounds by 703 and divide by height in inches squared.
How do I calculate BMI with pounds and inches?
Multiply your weight in pounds by 703, then divide by your total height in inches squared. The Imperial option above does this automatically, so you do not need to convert units yourself.
What is a normal BMI for adults?
For most adults, a BMI from 18.5 to 24.9 is considered the standard healthy range. A number outside that range is a prompt to consider more context, not a diagnosis on its own.
Is BMI accurate for athletes and bodybuilders?
BMI cannot distinguish muscle from fat. A muscular person may receive a result in a higher category even when their body-fat level is not high.
Does BMI use different categories for men and women?
The standard adult categories are the same for men and women. Body composition and health risk can still differ between individuals, which is why BMI should not be interpreted alone.
Can children or teenagers use this calculator?
No. People under 20 need age- and sex-specific BMI-for-age percentiles. This calculator uses adult categories only.
What should I do if my BMI is outside the healthy range?
A single result is not a diagnosis. If you are concerned about your weight, an unexpected change, or other symptoms, speak with a qualified healthcare professional for an individual assessment.
Evidence
Sources and scientific references
- World Health Organization: Obesity and overweight — adult BMI definition and standard category thresholds.
- Centers for Disease Control and Prevention: About BMI — BMI as a screening measure and its limitations.
- Centers for Disease Control and Prevention: BMI frequently asked questions — adult interpretation and contextual use.
Medical disclaimer: This calculator provides an estimate for general educational purposes. It does not diagnose a health condition or replace professional medical advice.