Anything less than that, and it's not considered a full bath. The size of your bathroom should be based on how many people you live with, whether they are adults or children. If you're renting, however, the landlord may not allow you to have a bathroom larger than 30 percent of the total square footage in the rental unit. If this is the case, then you'll need to share one bathroom with another tenant. In addition, the number of bathrooms available in an apartment or house complex can affect how much you will pay for rent. If there are a large number of units with only one bathroom, tenants will be forced to share or go without. On the other hand, if there are few bathrooms, you might have to pay more for an individual room. In most cases, the building owner will decide what percentage of the total floor area each bathroom should occupy. For example, a common rule is that each bedroom should have its own bathroom. This is because no one wants to sleep in a space that feels like a shower stall. If your apartment does not include these room sizes, you may want to ask your agent what standard practice is in your area so you don't pay more than you have to.