Adult BMI, height units, and category boundaries
Convert mixed feet and inches correctly, reproduce an adult BMI calculation, and understand why a rounded result does not determine its screening category.
Keep decimal feet separate from feet and inches
Five feet six inches is 5.5 decimal feet: the six inches are 6 ÷ 12 of a foot. It is not 5.6 feet. Enter whole feet and remaining inches in their separate fields. Use Height Converter when a form expects a different unit, then keep enough precision for the receiving calculation.
ADEMN uses the exact international conversion factors, including 2.54 centimeters per inch. The mixed output rounds inches to two decimals and carries into the feet field if the rounded remainder reaches 12. A converted display can therefore look slightly different after a round trip through rounded input.
170 cm
Expected result:
5 ft 6.93 in
1.7 m · 5.577428 decimal feet5 ft + 6 in
Expected result:
167.64 cm
1.6764 m · 5.5 decimal feet · 66 total inchesCalculate the ratio using meters
The adult BMI calculation is kilograms divided by height in meters squared. For 70 kg and 175 cm, convert the height to 1.75 m, then calculate 70 ÷ 1.75² = about 22.857143. The tool displays one decimal place, giving 22.9. Entering 175 as meters would produce a completely different ratio.
The age field checks that the person is at least 20; it does not change the adult formula. The tool uses CDC adult categories and does not provide the age- and sex-specific percentile calculation needed for children and teens. Samples use fictional measurements and are intended to explain the calculation.
Age 30 · 70 kg · 175 cm
Expected result:
BMI 22.9
Healthy weightClassify the unrounded result
The healthy-weight category starts at 18.5 and ends below 25. The next category starts at 25.0. Because the display is rounded to one decimal, a value just below a threshold can display the same numeral as a value at the threshold. ADEMN chooses the category before rounding the display.
The boundary example uses 76.5625 kg and 1.75 m, giving exactly 25. This illustrates the comparison rule; it is not a target weight or a suggested change. If another calculator gives a different category, compare its unrounded inputs and category rules before assuming a rounding error.
Age 30 · 76.5625 kg · 175 cm
Expected result:
BMI 25.0
Overweight
An illustrative threshold, not a recommended weight.| BMI, before display rounding | Category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 to below 25 | Healthy weight |
| 25 to below 30 | Overweight |
| 30 to below 35 | Class 1 obesity |
| 35 to below 40 | Class 2 obesity |
| 40 or above | Class 3 obesity |
Use the category with its limits
BMI is a screening measure rather than a diagnosis. It does not distinguish muscle from fat, describe fat distribution, or provide a complete assessment of an individual’s health. A health professional can consider measurements and circumstances that this ratio does not capture.
The tools keep entered age, weight, and height in the current browser page and clear them on reload. When reporting an unexpected result, use the provided sample or a fictional measurement, together with the selected units and expected arithmetic. A personal health record is unnecessary for reproducing a unit or rounding issue.