what size mirror for 72 inch vanity

For a 72-inch vanity, the maximum width of the bathroom mirror should be between 66 and 68 inches. This leaves 2 to 3 inches of space on each side of the mirror. However, a good rule of thumb is to have the mirror a few inches shorter than the overall width of the countertop whether you are using a single mirror or double mirrors for a double sink vanity.