BMI: read a screening number, not a health verdict
A result such as 22.2 can still leave questions: is it a percentage, and does it describe all of my health? Body mass index relates weight to height through a specific calculation. Understanding what it measures—and what it does not—is more useful than an unexplained number.
Use two measurements with consistent units
The metric calculation divides weight in kilograms by height in metres squared. Convert centimetres to metres before applying the formula by hand. The resulting unit is kg/m², not %.
Keep the original measurements beside a recorded result. A number without its height, weight and units is difficult to check. A height of 180 cm equals 1.80 m; entering 180 instead of 1.80 in a field that asks for metres is an input mistake, not a change in the body.
References: CDC — About body mass index
A screening category is not a diagnosis
The reference categories for adults aged 20 or older are: below 18.5, underweight; 18.5 to below 25, healthy weight; 25 to below 30, overweight; and 30 or above, obesity. A category name alone cannot assess an individual’s health.
Do not apply these boundaries to children’s or teenagers’ growth: their interpretation uses an age- and sex-related method. This is an educational explanation of adult categories, not a substitute for professional assessment.
References: CDC — Adult BMI categories and scope
Which questions does it leave unanswered?
BMI does not separate fat, muscle and bone, or locate body fat. It therefore cannot supply a body-fat percentage, a meal plan or a personal weight-change target.
If you have a health question about a result, discuss it with a qualified professional who can consider your measurements and health history. Use the number to explain the question, not to select treatment or judge yourself or others.
References: CDC — About body mass index
A calculation example, not a person’s assessment
For a fictional example, take a weight of 72 kg and a height of 180 cm, or 1.80 m. Height squared is 3.24, so 72 ÷ 3.24 = 22.222…; a typical display rounds this to 22.2 kg/m².
That does not mean 22.2% body fat. When comparing two apps, check the measurements, units and rounding first. More decimal places do not add a diagnosis or improve the original measurement.