Standard BMI
—
Traditional formula · height²
Same you.
A new perspective.
See standard BMI alongside the proposed new BMI formula. Enter your height and weight to compare the numbers instantly.
Your measurements
Choose whichever units work for you.
Calculations stay in your browser.
The comparison
LIVE RESULTSTwo ways to calculate body mass index.
New BMI
—
Trefethen proposal · height²·⁵
Your comparison will appear here.
Enter both measurements to get started.
The maths, made transparent.
Standard = weight (kg) ÷ height (m)²
New = 1.3 × weight (kg) ÷ height (m)²·⁵
In imperial units, the new formula is approximately 5734 × weight (lb) ÷ height (in)²·⁵. This calculator converts to metric first to keep results consistent across units.
Why do the numbers differ?
The new formula changes how height is accounted for. It gives a lower value above 1.69 m, a higher value below 1.69 m, and the same value at exactly 1.69 m.
Proposed by mathematician Nick Trefethen, it is an alternative calculation, not an established replacement for standard BMI.
A numerical comparison, not a diagnosis. Neither formula directly
measures body fat or muscle. Health categories are deliberately
omitted for the proposed formula.