I just had to get this off my chest.

[Evil Yoshi Toes]

That varies from game to game. In Mario odyssey he comes up to her eye level. So if we assume Peach is the average height for a woman by mushroom kingdom standards, that'd make Mario a very short guy. However, seeing that Luigi is considered tall but is usually shorter than or about the same height as Peach, maybe in the mushroom kingdom women are averagely taller than men. It's hard to say because we haven't seen a lot of humans there.
In Mario Sunshine he only comes up to Peach's breast, which makes him very short by real life man standards.

This is only counting his after-mushroom size since that seems to be his canon “normal” height, which means he actually shrinks when he's hurt rather than grows extra tall when he eats mushrooms. Both are equally disturbing if thought about too much.