What is the ideal hight for the toilet seet?

There is no correct or ideal height. Most are designed so that the actually seat without the lid is 17 - 18". Health advocates claim that the lower you are, the better your bodily functions work (squatting as our ancestors did, and much of the world still today), but as we get older, many people can't rise easily off of a low seat. Toilets are now made in higher models, or people buy 'donuts' that are molded plastic about 4" high that fits over the toilet with the seat up.