To identify the correct seat size for your toilet bowl, measure from the center of the mounting holes at the back of the bowl to the outside edge of the rim in front. A round bowl is approximately 16 ½” in length. An elongated bowl is approximately 18 ½” in length. View our Toilet Size Guide for more help.  Based on your measurement, order the appropriate seat – round or elongated – for your bowl. Our seats are designed to fit most manufacturers’ round or elongated bowls, even though there are some specialty sizes.  Please click here to view our video on how to determine the correct size seat for your bowl.