What is a one-and-a-half bathroom?

A one-and-a-half bathroom is a bathroom that contains both a toilet and a sink, but no shower or bathtub. However, it typically also contains a toilet and a sink, and may have a shower or bathtub if the space is large enough. The additional .5 is accounted for by the presence of a toilet, sink and shower/bathtub.

They are often found in small homes, apartments, and studio units, but they can also be used in bedrooms in large homes. One-and-a-half bathrooms are sometimes called "powder rooms" or "guest bathrooms.