While you might be tempted to buy a waterproof work boot that is the same size as your normal shoes, this isn't the best idea. As a general rule of thumb, you should always choose a boot that's large enough to accommodate an extra pair of socks. When trying on a new pair of boots, it's also important to factor in the thickness of your socks - you should choose a boot that's large enough to accommodate your socks without making the fit too tight.