These are ADA guidelines measured from floor to top of the seat:

A "standard" toilet height is 15 to 16 inches and best for adults under 5'4". The "comfort" height measures 17 to 19 inches from the floor for taller adults.

A basic rule of thumb is find one that your feet are comfortably planted on the floor while doing your business. Being left hanging isn't an enjoyable experience.

I have no idea, although I have seen some homes with small toilets but only adults living in the home. 

As far as I know, no regulations. I see them at all heights usually depending on when a house was built.

I have not done the measurements. 

Interesting question. I will have to ask a contractor friend. I have always taken toilet seat height as being “standard”. I have no idea what “standard” might be or if there is a “standard”.

Kevin J. May has your answer.

Fred Griffin - the loaded question and a good answer from Kevin J. May.

Preferred: Comfort height

ADA: Same as comfort height

Code: Only for commercial, not residential with regards to toilet height.  Both have standpipe requirements. Residential code does include closet specs for ADA. I'm fairly confident it's a 5' turning radius (for wheelchairs).

Had to make my handicap one 18 to 19 inches at my office.  I HATE it.  I'm 5 ' 4" so my private bathroom at my office is 15 inches.  Much better for me.

Not sure if there are particular standards for height and some do seem taller or shorter.. But this seems like it could be the perfect height for the right person.

Heights is very subjective choice, but water flow in it is regulated by retrofit and must be low flash in L.A. county.

I don't know about height, but we are dealing with making existing bathrooms ADA compliant at the association.  What a pain that is!

I'm flush without an answer on this. I don't think there are any prescribed values in AZ. But I know they come in different heights. Older ones seem to be lower, and newer ones much higher.

14" from the floor for standard

16" more comfortable height

19" handicapped....

might have changed now.... this is what I remember...

Water Conserving is the focus in my area.  Height for residential is not a concern ... that is personal preference. 

This is my preferred seat toilet height.

I do not believe we have any regulations on toilets yet, but we have seen much taller ones in the new homes.

What else can be said that Kevin May did not say?

It is in the local code, but that just mirrors the national recommendations.

Kevin has the answer.

The city and county do not regulate this. 

I refer to the right height as comfort height and know it immediately when I sit on it. But I am tall and my comfort might not be the next person's comfort.

Personal taste from what I have seen

Oh my, Fred,

You opened up quite a discussion.  I am speechless after reading the comments and seeing the photos.  LOL A

Fred Griffin I don't really know. Looks like Kevin J. May summarized the ADA requirements.

Have you noticed the increase in height created the need for  better evacuation efficiency.

So now we have Squatty Potty.

no clue

I just bought something recently and they made a point to mention that this is wheelchair compliant meaning a little taller than the norm. I recommend