Shoe sizes are gendered because men’s and women’s feet differ in more than just length. They differ in width, arch height, and overall proportions, and the footwear industry developed separate numbering scales centuries ago to account for these differences. The US system offsets women’s sizes roughly 2 numbers higher than men’s for the same foot length, so a men’s 7 and a women’s 9 fit the same length of foot but are built on different molds.
How Male and Female Feet Actually Differ
The case for gendered sizing starts with anatomy. A large-scale study of Japanese adults published in the Journal of Back and Musculoskeletal Rehabilitation found that compared to women, men had longer, wider, and higher feet, and that sex had a bigger impact on foot dimensions than either age or body mass index. In other words, the shape differences between a typical male foot and a typical female foot aren’t just about scale. A woman’s foot isn’t simply a smaller version of a man’s foot.
At the same length, women’s feet tend to be narrower, with a lower instep and a different volume-to-length ratio. The heel is often proportionally smaller. These differences matter because a shoe that fits well needs to match not just the length of your foot but its three-dimensional shape. Two people with identical foot lengths can need very different shoes if one foot is broader across the ball, higher through the arch, or narrower at the heel.
The Mold Behind Every Shoe
Every shoe is built around a solid form called a “last,” which acts as the foot-shaped mold that determines the shoe’s internal dimensions. Manufacturers use different lasts for men’s and women’s shoes, and this is where gendered sizing has the most practical impact.
A 2010 study that 3D-scanned 424 women’s feet and compared them to standard men’s running shoe lasts revealed a serious problem: many women’s athletic shoes were simply built on scaled-down men’s lasts. The width differences between these lasts and actual women’s feet varied by up to 9 mm. Length grading was close (less than 1 mm off), but width grading in the lasts was 3.5 to 5.9 mm larger than what women’s feet actually needed as sizes increased. The researchers concluded that using downgraded men’s lasts for women’s shoes should be questioned, because the proportional differences between male and female feet don’t scale linearly with length.
This is the core engineering reason for gendered sizing. If manufacturers used a single unisex last, one group would consistently get shoes that are too wide, too narrow, or poorly shaped through the heel and arch. Separate lasts allow each shoe to better approximate the typical foot shape of its intended wearer.
Where the Number Offset Comes From
In the US sizing system, women’s sizes run approximately 2 numbers higher than men’s for the same foot length. A women’s 9 corresponds to a men’s 7. Both fit a foot of the same length, but the internal shape of the shoe differs because it was built on a different last.
The Brannock Device, the metal foot-measuring tool found in shoe stores since the 1920s, captures three measurements: total foot length, arch length (heel to the ball of the foot), and width. The formula converts these raw measurements into a numbered size, but uses a different starting offset for men and women. Men’s sizes begin calculating from a baseline of 7⅓ inches, with each size adding a third of an inch. Women’s sizes use a different baseline, producing the familiar 1.5 to 2 size gap. Width is measured on a letter scale from AAAA (narrowest) to EEEE (widest), and the actual millimeter range assigned to each letter also differs between men’s and women’s scales.
A System Dating Back to 1688
Gendered shoe sizing isn’t a modern marketing invention. The earliest recorded sizing system appears in a 1688 text called The Academy of Armoury and Blazon by Randle Holme III. He described children’s sizes running from 1 to 13 (the “short thirteens”), starting at five inches and adding a quarter inch per size. Adult sizes, which he called “the long size or Man’s size,” picked up where children’s left off, running from 1 to 15. At that point the system grouped men and women together, but the foundation of scaling by quarter-inch increments and separating children from adults was already in place.
As mass manufacturing grew through the 18th and 19th centuries, shoemakers needed standardized sizing to produce shoes without measuring each customer individually. The growing understanding that men’s and women’s feet differed in proportion, not just length, pushed manufacturers to develop separate scales. The US, UK, and several other countries adopted gendered numbering. Each country chose slightly different formulas, which is why international size conversion charts exist.
Why European Sizes Work Differently
Not every system uses gendered numbers. European (EU) shoe sizes are gender-neutral. A size 42 is a size 42 whether the shoe is marketed to men or women. The EU system measures the length of the last in units called Paris points (each equal to two-thirds of a centimeter) and applies the same scale regardless of sex.
This doesn’t mean European shoes ignore anatomical differences. The number on the box is the same, but the last used to build a women’s EU 40 still differs in width and shape from a men’s EU 40. The gendering happens in the construction, not the labeling. So while EU sizing simplifies cross-shopping (you don’t need to do mental math converting between men’s and women’s numbers), the physical shoes are still designed for different foot shapes.
Biomechanics Beyond the Foot
Some shoe designers also account for differences higher up the body. Women have a slightly larger Q-angle, which is the angle between the thigh bone and the shinbone at the knee. The average Q-angle is about 14 degrees in men and 17 degrees in women. A larger Q-angle shifts how forces travel through the leg during walking and running, potentially affecting how the foot strikes the ground and how much inward roll (pronation) occurs.
The traditional explanation is that women’s wider pelvises create this larger angle, though research has complicated that story. Studies measuring actual pelvic width find it’s surprisingly similar between the sexes when you account for body size. The Q-angle difference may come from other structural factors rather than pelvis width alone. Still, some performance footwear brands use the Q-angle difference to justify different cushioning densities or support structures in men’s versus women’s shoes, going beyond just sizing into genuinely different engineering.
What This Means for Shoe Shopping
If you’ve ever grabbed a men’s shoe in your converted size and found it fit strangely, the offset number isn’t the problem. The last is. A men’s 7 and a women’s 9 share the same nominal foot length, but the men’s shoe will typically be wider across the ball, roomier through the midfoot, and broader at the heel. For some people this is actually preferable. Women with wider feet sometimes find men’s shoes more comfortable, and men with narrow feet sometimes do better in women’s models.
The gendered system works as a useful population-level shortcut. It routes most shoppers toward shoes shaped closer to their likely foot proportions without requiring everyone to get a 3D foot scan. But feet vary enormously within each sex, and the “average” male or female foot is a statistical abstraction. Width letters (B, D, EE, and so on) exist precisely because a single gendered last can’t capture all the variation within half the population. If your feet don’t match the standard proportions for your assigned size category, crossing over to the other category or seeking width-specific options will often get you a better fit than forcing a number conversion.