The height will depend on the cultivar. For instance, I have grown the cultivar "Alaska" from seed and they are huge, 36-40 inches tall. I also have the cultivar "Snow Lady" growing with my daylilies and it is about 18-inches tall (about the height of the fans of the larger daylilies). There is another cultivar I'm looking at for the edge of beds, "White Breeze" that is supposed to only grow about 12-inches tall. There are many, many cultivars now available on the market, seeds or plants, so you should be able to fine one (or several) that will be able to meet any need you have.
The height will depend on the cultivar. For instance, I have grown the cultivar "Alaska" from seed and they are huge, 36-40 inches tall. I also have the cultivar "Snow Lady" growing with my daylilies and it is about 18-inches tall (about the height of the fans of the larger daylilies). There is another cultivar I'm looking at for the edge of beds, "White Breeze" that is supposed to only grow about 12-inches tall. There are many, many cultivars now available on the market, seeds or plants, so you should be able to fine one (or several) that will be able to meet any need you have.