Half a shoe size does make a difference and can be noticeable and impactful, especially for fit and comfort of the shoe.
If the shoe is half a size too small it can lead to pain and discomfort and if the shoe is 1/2 a size too big it may try to come off your feet when walking.
A half a size in shoes seems small, although it also translates to around 1/8 inch in width and length, which can significantly affect how the shoe feels and how well the shoe supports your foot, especially when it comes to running shoes or shoes that are worn by kids.
The rule of thumb for shoes is that you should choose a shoe that has about a 1/2 inch or a thumb's width of space between the end of your longest toe and the end of the shoe.
This is to allow for natural foot movement and to prevent blisters and discomfort from shoes being too tight.
Socks also can affect shoe size, especially when you're wearing thicker shoes.
The thickness of your socks can make a shoe feel tighter or more loose.
If the socks are thicker then your shoes may feel more tighter than they would with thinner socks.
Wearing thicker socks adds volume to your foot and makes your foot seem larger which can affect how the shoes fit.
So if you're wearing thicker socks you often need to wear bigger shoes to accommodate the thicker socks you're wearing.
And when wearing thinner socks you may need to wear a slightly smaller shoe size to accommodate the thinner socks.
The extra padding of the socks makes your feet slightly larger than they would be when they are bare without socks.
The extra padding of the socks needs to be taken into account when measuring up for new shoes and when you're trying the shoes on as well.
Socks can also add anywhere from a 1/4 inch to an inch or more to your height depending on the thickness of the socks and the style and thickness of the socks.
Thicker socks such as boot socks, can add more height than thinner socks like shorty socks.