Methodology
Transparent adult BMI calculation formula, conversions, ranges, and known limitations.
Core equation
BMI = weight in kilograms ÷ (height in meters)². The calculator uses this equation for both unit systems after converting inputs to kilograms and meters.
Conversions used
1 pound = 0.45359237 kilograms. 1 inch = 0.0254 meters. Feet are converted to inches by multiplying by 12. Metric centimeters are divided by 100 to obtain meters.
Displayed precision
BMI and reference weights are shown to one decimal place. Calculations use full-precision JavaScript numbers before rounding for display. Because categories are computed from the unrounded BMI, values very close to thresholds may be classified using the precise result.
Reference weight computation
For a selected height, the mathematical weight at a given BMI equals BMI × height in meters squared. We show values at BMI 18.5, 24.9, and 29.9 to help visitors compare reference points.
Input checks and privacy
The interface rejects nonpositive and implausibly large values. The tool calculates locally in the browser; it does not submit entered height or weight to a BMI calculation server.
Limitations and sources
The adult categories follow common public-health screening conventions. BMI does not assess body composition or diagnose disease. See CDC Adult BMI Calculator and CDC About BMI.