(For each shoe, manufacturers create a series of lasts, solid pieces of wood or other material around which the shoe is constructed. The last determines the interior shape of the shoe.)
A few other nuggets of info come out of the above formulas:
1) A U.S. shoe size equals only a third of an inch. A half-size is a mere sixth of an inch.
2) If you add 1.5 to a men’s shoe size, you get the women’s shoe size equivalent. Or if you subtract 1.5 from a women’s shoe size, you get the men’s equivalent. For example, a size 9 men’s shoe is the same as a women’s size 10.5.
3) Size is determined by last length, but the actually interior length can vary depending on how the shoe is then constructed around it. If there are small gaps between the front or back of the shoe and the last, it will consequently run big. (Remember we’re talking about fractions of an inch here.) Shoes built precisely to the length of the last are usually considered to run small.
And one final bizarre factoid for shoe sizes: The base metric for U.S. sizing comes from an archaic English unit of measurement known as a “barleycorn,” which is equal to a third of an inch.
Variable Foot SizeMost people don’t realize that one of their feet is slightly larger than the other. It’s true for the majority of the population, though the difference is seldom more than a single shoe size (or a third of an inch as discussed above). When trying on footwear, always fit the larger foot.
Flattening FeetOur feet slightly lengthen over the course of our adult lives. Your feet don’t grow any longer, the ligaments and tendons simply stretch out and flatten slightly, which translates into a slight increase in length. The average person’s feet gain a full size over their lifetime.
This phenomenon can be more pronounced for people who spend a lot of time on their feet and for people who are overweight.
“Equipped” is an AMC Outdoors blog, written by Matt Heid.