Commercial ADA compliant restroom design requires the consideration of many factors. The details of these requirements are covered in the 2010 ADA Standards for Accessible Design | ADA.gov document. State and local requirements may also apply.
While you digest the finer points of the ADA requirements, here are details on the smallest permissible wheelchair and ambulatory accessible toilet compartments based on the national requirements. This article will also note where larger dimensions may be required. More thorough discussions of ADA requirements for bathrooms can be found in our ADA Bathroom Requirements - Adult Toilet Partitions and ADA Bathroom Requirements – Children's Toilet Partitions articles.
The following figure, taken from Figure 604.8.1.1 of the ADA Standards, illustrates the minimum permissible clearances.
In practice, most ADA wheelchair toilet partitions are laid out to be at least 60 inches wide and 60 inches deep. This makes them ADA compliant for any of the above three scenarios,
Ambulatory accessible stalls have both minimum and maximum dimensional requirements. The ambulatory requirements do not differ for adults and children.
The following figure, taken from Figure 604.8.2 of the ADA Standards, shows the permissible dimensions for ambulatory compliant stalls.
Some factors may require the above to be enlarged or modified. Examples of this include projecting obstructions (like baby changing stations), approach requirements, toe clearance requirements, and floor space around the stall. Please refer to the ADA Standards for a complete list.
If you are tight on space, now you know the national limits.