The proper size of your bathroom mirror will typically be dictated by the size (width) of your vanity countertop. A good rule of thumb followed by designers is at least 2 inches smaller in width than the vanity, and in most bathrooms more like 4 to 6 inches. This provides at least 1 to 2 inches on each side of the bathroom mirror and eliminates “the box” look that automatically cheapens the design of your entire space. After determining the measurement that helps you determine how wide your mirror is you must consider the height. A bathroom mirror should be no taller than your vanity and placed at least 4 to 6 inches from the ceiling. If lighting is located directly above the mirror space then this must also be factored into the height of your mirror allowing for approximately 3 inches between the top of the mirror and the bottom of the light fixture for optimal lighting.