If the discharge hole opening looks about the size of a baseball or an orange, you have a 2-inch toilet. If it looks about the size of a softball or a grapefruit, you have a 3-inch toilet. Alternatively, if your toilet has a rubber flapper, measure across the flapper. A 2-inch toilet will measure a little larger than 2 inches, while a 3-inch toilet will measure a little larger than 3 inches. By knowing the size of your toilet, you can ensure a perfect fit and optimal performance with our Smarter Flush products.