What Is My BMI?
You need two numbers, height and weight, and about 30 seconds.
To find your BMI, divide your weight by your height squared: kilograms divided by meters squared, or 703 times pounds divided by inches squared. A 150-pound person at 5 ft 6 in gets 703 times 150 divided by 66 squared, which is 24.2, a healthy BMI. The calculator above does the arithmetic and shows your category and healthy weight range automatically.
The 30-second method
Pick your units, enter height and weight, and read the result. The calculator handles the unit conversion constant for you, so you never touch the 703 or the squaring yourself.
Write the number down with the date. A single reading is a snapshot; the trend over months is what actually tells you something.
What your number means
Below 18.5 is underweight, 18.5 to 24.9 is healthy, 25 to 29.9 is overweight, and 30 or above is obesity. Each band is a risk signal from population data, not a personal diagnosis.
Context changes the reading. Athletes, pregnant women, older adults losing muscle, and growing teens all need a different lens, which is why the number is a starting point.
What to do with the answer
If you landed in the healthy band, the job is maintenance: steady activity, reasonable food, and a recheck now and then. If you landed outside it, decide one small change, not ten.
If the number worries you, bring it to a clinician along with your waist measurement and activity level. That combination beats any single number.
Skip the arithmetic
Find your BMI in 30 seconds with the free calculator.
Finding your BMI questions
How do I find my BMI without a calculator?
In imperial units, multiply your weight in pounds by 703 and divide by your height in inches squared. In metric, divide kilograms by meters squared. A phone calculator handles either in under a minute.
Do I need my exact height?
An inch of error moves BMI by roughly half a point, which rarely changes the category. Still, if you plan to track the trend, measure your height once properly so every reading is comparable.
How often should I check my BMI?
Monthly is plenty for tracking. Weight swings a few pounds day to day from water and food, so daily BMI checks add noise, not insight.