Measure for a new toilet by checking the rough-in distance from the wall to the center of the drain bolts. Standard rough-in is 12 inches. Measure the available space width to ensure the new toilet fits between walls or cabinets. Note the bowl shape preference round or elongated. Elongated bowls extend about 2 inches further into the room. Check the water supply valve location and measure seat height preference. Standard height is 15 inches while comfort height is 17 inches.