Do you REALLY know your shoe size?

Most "normal" fitting people could probably go half size down and one width up

Same here.  I was wearing a size too large (and a width too narrow) until I bought my first pair of decent shoes.

My feet are different sizes so I'm always either a half size large or a half size small on one foot or the other. Frustrating. I usually go a half size up and just tighten the one set of laces more. Makes loafers tough.

So true! I always used to buy size 11.5D/12D. The first time I went in an Allen Edmonds retail store, they suggested I get measured. Turns out, I am a 10.5EEE... It's a life-changing moment, honestly.

Most people have different sized left and right foot, with leading foot smaller and wider.

Yeah, I always thought that I was an 8E or something because I thought I had wide feet. I got measured at turned out I'm actually 8.5C on the right and 8C on the left. I still end up buying 8D's though as they feel the most comfortable to me and C widths are pretty rare to come by.

Yes I do, 45 is the correct size for my feet.

haven't you ever sized your feet using a Brannock device? it's not 100% accurate when determining last size/fit but it's in the ball park. i'm stating the obvious here but different shoes fit differently. my foot measures a 9D on a Brannock device - I wear a 10D tennis shoe and a 9D dress shoe

I measure a 8.5 - 9 on the Brannock device but I feel most comfortable in Allen Edmonds 7.5EEE. I typically find that most dress shoes have way too much toe space for my liking for the Brannock measurement. The ball of my foot always lands way to far back in the toebox which makes for uncomfortable walking. It's definitely important to actually try shoes on and be honest with yourself in regard to how comfortable they are.

I buy my shoes based on what the Brannock gives me and since starting I've nailed it every time. Basic rule of the Brannock is to take the same length or go down 0.5 sizes. This depends on what shoe is in question (British shoes are different from most US shoes in this logic). The width is always rounded up if you are in between widths or, for example, a "C+".
 

Brannock gives two length measurements, maybe your heel to ball size is that different than foot length...

Every manufacturer has a set of lasts that they work off of. But lasts have to be made...initially, by hand, to create a "prototype," and then turned to specified size(s) to end up with the lasts that the maker uses..

While there is a rough standard for sizing in the industry, the prototype can be labeled to be any size that the manufacturer desires. And all turned lasts in that model will be sized accordingly. It's just a number. IOW, the size is what the company says it is.

The reason that Brannock devices are inaccurate...and more than just occasionally...is that foot length has less to do with what size shoe/or last is appropriate for your feet than the heel to ball measurement. All too frequently, neither shoe salesman nor manufacturers take that measurement into consideration. IIRC, a Brannock device can take the heel-ball measurement but what to do with it once it is taken? There is no readily available information that compares H-B to last/shoe size. [It's actually a lot more complicated than it sounds ]

So foot length is used to fit a shoe. And since each manufacturer has a last model that may be "graded" as much on the basis of whimsey as rationality, you may easily and frequently find yourself in a size 9 for one manufacturer, and/or last model, and a size 8 in another brand/model.

It might be worth considering that while you are young and full of juices your feet may seem to accommodate themselves to an improper fit. No pain, no worries. But as time goes by you can do irremediable damage to your feet by wearing even a half size too long or esp. too short. And when you get old nothing short of orthopedic shoe will ameliorate the discomfort.

In the future I will take note of the heel to ball measurement. I wasn't aware of it. I have a high instep so I think that may be the cause of my fit issues. The ball of my foot is probably a bit closer to my heel than the average person.