Napoleon's recorded height of "5 pieds 2 pouces" was measured in pre-metric French units, not modern English feet and inches. When correctly converted, that figure equals roughly 1.67–1.69 m — around 5'6" to 5'7" in today's terms. Encyclopædia Britannica and History.com both explicitly identify the confusion between French and English measurement systems as the origin of the myth.
For context, PubMed anthropometric data on French military recruits and historical records cited by the University of Chicago's "Health and Welfare during Industrialization" place the average French adult male of the late 18th and early 19th centuries at approximately 1.64–1.65 m. That means Napoleon was at or slightly above the average height of his contemporaries, not below it.
British propaganda — particularly caricatures by cartoonist James Gillray — also played a major role in cementing the "short Napoleon" image in the popular imagination. Because the English "inch" is longer than the French "pouce," a direct but incorrect substitution of units makes Napoleon appear to be only about 5'2", fueling the misconception that persists to this day.