Standard Bathroom Cabinet Height. Otherwise, it will feel too short for adults or too tall for kids. It's really up to you and your bathroom preferences.
A bathroom countertop may be slightly less high. Your hand should easily reach the top of the cabinet. Use them as a starting point and feel free to adjust them to fit your space and to accommodate the users of the space.
To get a good idea about these vanity heights we need to look into them in much more detail.
I think the entire bathroom fitting layout depends on the size of the vanity you choose.
Keep in mind that these are just the standard measurements. Although heights may vary, it is important to remember that the higher the bath is, the harder it is to get in an out. Your hand should easily reach the top of the cabinet.