Measure Vanity Width
Grab your tape measure and measure the width (side-to-side) of your current vanity or the space you intend to use. Measuring the width is key to determining how much physical and visual space your vanity will take up in your bathroom. Keep in mind that vanity tops typically add ½ inch to 1 inch more on either side of the cabinet width.
Tip: Building codes often require at least 15″ from the center of your toilet to any fixture. Check your local code to be sure your new vanity meets all requirements.