Hmm, I search for better fit (eg cut wider in the body but still with correctly placed shoulder seams) rather than size up. A true size up on me generally looks just that: like my clothes are too large.

Some sizing up in tops and footwear and loungewear— but what Liesbeth said .
Not sue is “ sizing up” or “ right- sizing”!
I do like a more fluid fit in tops so a lot of my tops are M or sometimes L when you’d think that would not be my size. but I have to be careful or the armholes and shoulders will be too big. So I have to make myself walk away if the sizing and fits don’t work right.

I’m kinda sizing DOWN in pants- not really per size itself, but watching fits more. I used to buy them too roomy or accept cuts that were not quite right and that looks more frumpy on me.

Lounge/ Pj’s though— need roomy but again, I’ve passed by some that just didn’t look right in either the fitted or roomy size. Trying to be more picky.

What kkards said. In my 20s and 30’s I was size 8 shoe, after kids 8.5, another few years (and lbs!) and I’m an 8.5 or 9 and I go 9.5 for running shoes and sometimes booties? The years take a toll, and sizing could be different too. And as another poster said one brands size 8 is another brands size 12 as far as fit.

I don't like a snug fit in most things so I guess I size up, but definitely in boots because I like to have some wiggle room. Also pj's as has been mentioned -hate a tight waist more than anything!

What is size? On any given day, I can be wearing on the same body, at the same time, any size from XS to XL. A tight cami? I size up to L or XL or else it will ride up and be annoying. My new raincoat is Petite L (based on careful reading of reviews) and it fits exactly right through the body, waist and shoulders. My new casual knit jacket is size XS. How does this make sense? I don't worry about it! It is what it is. My pants size is generally consistent, my shoe size, if the shoe works with my low volume, fussy feet, is usually consistent.

Shoes, yes: boots, because of my high and sensitive instep, both to get my foot in and out, and for comfort; pointy toes IF the shoe is otherwise comfortable and fits well, because my toe box is also wide. Selecting my normal shoe size in a wide width generally doesn’t help, because then it’s too wide in the wrong places.

Also athletic shoes and hiking boots, because toe bruising is not a good thing, and feet swell with a lot of exercise/running/hiking.

Camisoles sometimes depending on the material and cut so I can get a good fit in the bust.

For me it really depends more on the fit of the item. As I've aged, I've learned that what the tag says doesn't matter. Try it on. If I need to go up a size, I go up; if I need to go down a size, I go down and don't assume it is because I am actually that size.

I guess I know what feels right and how I want something to fit, so I don't automatically size up in anything. I try it on and decide from there. If the size I normally wear doesn't fit, I assume it runs big/small and choose a different size. I don't assume I need a larger size in anything without trying.

It's always funny to me to read reviews that say the reviewer LOVED an item but returned it because their usual size was too small. Not "exchanged it for the next size up" but returned it.

I size up lounge wear, workout gear (like lisap I don't like super tight workout tops), and shorts. It's hot when I wear shorts so I like them a little roomy - it's cooler and more comfortable in the heat.