Dimension of a Restroom
Restroom specifications may differ depending on the country of origin. 
Keep in mind too the restroom dimensions in residential homes will differ from those in commercial buildings. If you are designing a restroom, the following factors may be considered.
Floors per Building
The floor levels will determine restroom size. Assuming it is a single story house, the dimensions can be set at 2 x 3 meters. This figure is good enough for a floor area measuring 70 sq m, but if there are other floors, the dimensions will have to be increased. Or you can add another restroom on the other floors.
How Many Rooms per Floor?
A 70 sq m space can hold 3 rooms. Keeping this in mind, 6 sq m (2 x 3 m) restroom dimensions will be sufficient. If you want to make two bathrooms, you can make each one 1.5 x 2.5 meters. But if the area is bigger than the one specified, the comfort room will have to be much larger.
For example, a department store with a floor area measuring 600 sq m can hold up to a dozen stalls 20 x 30 m each. Each of these should have at least a couple of toilet cubicles. The size of course, will be determined by the number of amenities included in the room.
Proportion is Important
When considering the restroom dimensions, its relationship with the whole edifice must be accounted for. The average ratio is 20% to 30% is to 70% to 80%. Anything beyond this and the restroom is already out of proportion.
The proportion must be assessed thoroughly as an overly large restroom can be quite unsightly. There are exceptions to this rule of course, as when the whole building is to be used as a restroom.
Tips for Public Restroom Design
For public restrooms, make sure the partitions are high enough so eye contact is avoided. The partition must be high enough to hold in the urine splashes and provide privacy. For women’s public restrooms, set the entrances so those in line can see the stalls.
When assessing the restroom dimensions, ensure the hand dryers and the sinks are placed apart from the stalls. This will keep traffic to a minimum, particularly with crowded bathrooms.
Position the Door and Mirrors Carefully
A designer should review the placements of mirrors. You must avoid placements that may offer views into private areas. This is particularly important in women’s restrooms.
Check the Local Law
States and cities may have specific regulations on the building and maintenance of public restrooms. For example, there may be rules on how often the room is cleaned, the use of hot water etc.
For example, women’s airports restrooms in Atlanta must be cleaned continuously from 7 AM to 11 PM. This is besides the full cleaning at midnight.
The restroom dimensions must be given careful consideration, whether it is for public use or for at home. There must be appropriate spacing for people to move in and out comfortably.
