It is common for your left and right feet to be slightly different sizes to each other. This doesn’t mean that your feet are different shoe sizes (although that can happen), just that they’re not quite a mirror image of each other.
Let me explain.
Almost all human beings – perhaps all – have mismatched feet (sometimes called “mis-mated feet”); that is, one of their feet is different (usually very slightly different) in size, shape or proportion to the other.
So while your feet might take the same shoe size they are actually not 100% identical.
How could this be?
Although the human body looks symmetrical, almost all people have an inherent preference for one side of a pair of body parts over the other. Most significantly, this occurs in “handedness” – that is, being left handed or right handed.
However people also have dominant eyes, legs and other body parts. These can all inter-relate for reasons we don’t yet fully understand.
For example, a 2021 study concluded that there was a “significant association” between a person’s dominant hand and dominant eye. This was not a complete mapping of one to the other, though: the authors also concluded that at least 20% of people will prefer to utilise one hand and the other eye.
Also in 2021 a study found that certain Australian parrots with stronger left-foot preferences had larger brains than right-footed ones.
But what does this mean for your foot size?
It means that looks can be deceiving. Just because our bodies look symmetrical doesn’t mean they are.
It is actually is completely normal to have one foot that is bigger than the other. Or one foot smaller than the other, depending on how you look at it.
In September 1983, shoe expert William Rossi concluded that “All Americans, and most likely all individuals in all societies, have mismated feet; that is, the two feet of probably no individual are exactly alike in size, shape, or proportions.”
Rossi based his conclusion on a demographic foot-measurement “survey” embracing 6800 adults (4000 females, 2800 males), conducted in 1981–1982 by the Prescription Footwear Association.
However there is little independent evidence to back up this claim and Rossi may have been overstating things somewhat.
A 1988 study measured the foot and shoe sizes of 51 female Japanese university students. The study found that the average foot length was 22.8 cm for the left and 22.9 cm for the right. This meant that the right foot was, on average, 0.1 cm (just less than 0.04 inches) bigger than the left foot.
(Other people claim that left feet are more likely to be bigger than right feet, but there does not appear to be any data that backs this up.)
Importantly, the study found that one third of the students (33%) had identical right-left foot lengths.
We could conclude from this that only two-thirds of the population have different sized feet. However, the sample size is far too small to draw any real conclusions.
There is one conclusion of which we can be sure: most people must fit the same size shoe on each foot because the demand for different sizes in “pairs” is very small indeed.
In fact, many people won’t even notice that their feet are different sizes. And even if they are, the chances are that it won’t much matter.