BMI at the Height Extremes
Squaring height in the BMI formula corrects for most of the natural relationship between height and weight. It does not correct for all of it — some research points to a small, predictable drift at the far ends of the height range.
Two worked examples, same body shape
152 cm, 52 kg
BMI 22.5
198 cm, 88 kg
BMI 22.4
Both examples describe a proportionally similar build at very different heights. The formula keeps both in a comparable range — evidence the height-squared correction works reasonably well even outside the average height band, though not perfectly at the true extremes.
Why the correction isn't exact
Quetelet found that squaring height gave the best statistical fit across the population data available when he developed the formula in the 1830s. Body proportions do not scale perfectly with the square of height across every part of the height distribution, which is why some researchers have proposed adjusted exponents for people at real extremes. None of these alternatives has displaced the standard formula in general use.
Common questions
- Does height affect BMI accuracy?
- Squaring height in the formula corrects for most of the relationship between height and weight across the typical adult range. At the extremes — very short or very tall — some research suggests the correction is imperfect, tending to run slightly high for shorter people and slightly low for taller people.
- Why does BMI use height squared instead of height alone or height cubed?
- Quetelet found that squaring height gave the best statistical fit to weight across the population data available at the time. Height cubed would match the geometry of a three-dimensional body more closely, and some researchers have proposed adjusted formulas for this reason, but height squared remains the international standard.
- Is a very tall person's BMI likely to read too low?
- Some research suggests standard BMI may modestly underestimate body fat in taller individuals and modestly overestimate it in shorter individuals, though the effect is generally small for most adults and becomes more noticeable only at the extremes of the height distribution.
- Should short or tall people use a different formula?
- For most people, the standard formula remains a reasonable estimate. Alternative formulas exist for the small percentage of people at real height extremes, but they are not in wide clinical use, and pairing standard BMI with a body composition measure addresses the practical gap for most people.