The height categories
Standard / Round-Front Standard (14-15 inches): the traditional height, dominant in pre-2005 US homes. Floor-to-top-of-seat measurement of 14-15 inches.
Comfort Height / Chair Height / Right Height (16-17 inches): the modern default in new construction. Manufacturers use different marketing names but all refer to ~17-inch floor-to-seat. Easier for adult use; ADA-compliant minimum.
ADA / Universal Height (17-19 inches): the accessible-bathroom standard. Includes the toilet seat in the height measurement (typical seat adds 1/2 inch).
Tall / Extra Tall (18-20 inches): specialty models for users above 6\'2" or with specific mobility limitations. Kohler "Highline Tall" and similar specialty SKUs.
What height is right for whom
Children under 8: Standard 14-15". A taller toilet means feet dangle, which is unstable and uncomfortable.
Adults under 5\'8": Comfort (16-17") is generally comfortable, but standard works too. Test by sitting in a showroom if possible.
Adults 5\'8" to 6\'2": Comfort (17") is the sweet spot for most people in this range.
Adults over 6\'2": Tall (18-19") may feel more natural — though comfort is also fine.
Users with knee or hip issues: Higher is better. Comfort minimum; tall if mobility is significantly limited.
Users in wheelchair-accessible bathrooms: ADA height (17-19"), which matches average wheelchair seat height for transfer.
The aging-in-place argument
For any household with adults over 60, or planning to age in place: comfort height or taller. Bathrooms are the #1 location of home falls for older adults; the standard 14-inch toilet is a meaningful contributing factor (it requires more knee bend and balance to use). Switching to 17" is a cheap, high-impact aging-in-place upgrade.
How to measure
Standard practice: measure from the finished floor to the top of the porcelain bowl (without seat). Add 0.5 inch for the typical seat thickness. Some manufacturer spec sheets give the dimension with the seat included — verify which they\'re quoting.
Seat thickness variation
Most molded plastic seats add 1/2 inch to bowl height. Heated/bidet seats add 2-3 inches because of the internal mechanisms. If you\'re adding a Washlet C100 or similar bidet seat to a comfort-height bowl, you bump the effective seat height to 19-20" — which suits taller adults but may be uncomfortable for shorter users.
Mixing heights in one household
If the same bathroom is used by both kids and adults, comfort height (17") is the better compromise — kids can use it with a stool for foot stability; adults are comfortable. Standard (14") is too low for adults to sit comfortably for 5+ minutes.