Most home bathrooms will place the bathroom outlet 2-4" above the back splash for the vanity. The NEC does not specify a height requirement only that one receptacle outlet must be placed within 3 ft of the outside edge of each vanity basin.
Height is only one consideration when thinking about bathroom outlets. The number of bathroom outlet receptacles to add should be considered as well.
How Many Outlets Should I Add in a Bathroom?
The NEC code only specifies a minimum number of outlets based on the number of wash basins you will be installing. If you have one sink, you need at least one outlet.
Considerations for USB Outlets In Your Bathroom
If you are in the process of adding or changing outlets in your bathroom, one thing you may want to seriously consider is adding USB charging capability to your vanity outlets. GFCI outlets are not available with USB ports.
What Height Should Bathroom Switches Be?
If placed on a blank wall, bathroom switches should be the same height as every other switch in your house. When being placed above a vanity, height is at your discretion.