I recently had to buy new work out shoes. I don’t normally wear sneakers for any other purpose, I don’t care what they look like, so I don’t buy often. I had last bought two pairs of size 12 (New Balance if it matters) about six years ago that fit until I wore the soles out. I am 36 and have been a size 12 since I was a teenager. I did just buy dress shoes and casual shoes and those were still size 12, but when I tried on cross trainers, all of the size 12s were too small across all the brands. I had to move to 13s and they felt the same as my old 12s. Has anyone else noticed this? Or have my feet started growing again?
Sizes seem to vary by brand. For example In Adidas I’m a size 12, but Nike I’m 13.
If you have had the same shoes for six years you’ve probably stretched them out quite a bit. The new ones that feel too small may just need some breaking in.
That was what I thought at first, too. But I went through at least four major brands (Nike, Asics, New Balance, Addidas).
I might have thought that if they just felt snug, but they were too short for my toes.
How old are you? As I am getting older, my feet have grown (based on trying on shoes that fit 15 years ago.
I think you probably had ‘worn in’ your shoes so they expanded as your feet did and that sizing hasn’t changed.
In the 70’s and before, shoe sizes were rather consistent. Athletic shoes were made in America and some in Japan. I could wear a 9.5 in some cases back then. Gradually the Chinese took over the market and the sized began to grow. In other words, I needed a 10>11>11.5. One theory was that they were getting paid more to manufacture bigger sizes so the made everything with a bigger size number for what was formerly a smaller shoe. Withing the last year or two, this size creep has started to reverse a bit. I’m back to a solid 11.
PS> You can hold different brands sole to sole and observe that the same marked size is often different from actual. This is why shoe salesmen learn to say, “that brand runs small” and such statements.
I haven’t noticed a difference myself. I’ve always been 9.5 (well, really between 9 and 9.5) and I buy new athletic shoes yearly, across a wide range of brands (Asics, Brooks, Adidas, Nike, Converse.)
I do think something may be going on (then again, that something might be my feet getting bigger over time). 
I was a consistent 9.5 for most of my adult life. Over the past 5-6 years, I discovered that 9.5s didn’t fit well anymore, and I had to move up to 10s (particularly when being fitted for shoes by sales staff at stores who actually knew what they were doing).
Both foot size and shoe sizing changes over time. Your feet can grow a bit simply with age, but especially with weight gain (and pregnancy).
I’ve found that shoes are undergoing ‘vanity sizing’ or a general size inflation, same as most brand-name clothing. People and their feet are bigger. These days I’m most often a 7 or 7 1/2 when I try on new shoes. When my feet stopped growing in 6th grade, I was an 8 or even 8 1/2 in most brands.
I can’t speak to athletic shoes though, I’ve never really worn them. Or men’s.
I figure that the indestructibility of the Brannock Device should keep vanity sizing in check to some extent.
Never noticed it myself. My size 14 flippers have always fit well in size 14 sneaks of many brands.
In the years from age 18 to age 65, my shoe size has gone from 9D to 11EEEE. As you age, especially if you’re barefoot a lot like me, your foot spreads, and possibly your arch falls a little too. Weight gain is another factor; your feet get fatter just like almost everything else.
The New Balance dealer in northern Marion County/Indianapolis does not even have a Brannock Device. The difference among shoemakers varies so widely that standard sizes are obsolete. I wear a 13dd in NB, a 14m in Air Jordans, and a 12 w in another brand. Most brand make only one width.
What composer had the narrowest feet? Gabriel aaaa!
This. Your feet change shape subject to weight changes, types of activities engaged in, types of shoes worn regularly, time spent barefooting, etc. It boggles my mind that people expect their feet to stay the same size throughout their lives while the rest of their body changes greatly, especially given the amount of use feet tend to get.
Also, American shoe sizing is very imprecise and there is no standard length for lasts, nor does every design fit the foot the same. Further, there is more than one system for determining shoe size and once again, no standardization across manufacturing.
From ages 15-40, my shoe size has gone from an 11M to 13M. It’s really more for the width than the length, though … the right 12-wides will still fit well. But if I want a shoe to fit comfotably right out the box, with minimal break-in … it’s gotta be 13s.
That goes for athletic shows, casual shoes, and dress shoes.