According to House Plans Helper, a full bathroom should have minimum dimensions of 5 feet by 8 feet. This minimum size allows for a standard-size bathtub along with a sink, toilet and swing space for the door. For a half bath, minimum dimensions are 5 feet by 3 feet.
A standard-size bathtub is 5 feet by 2.5 feet, with 30 inches of clear space recommended along the edge of the tub. For the toilet, a 40 inch side-to-side span is recommended, along with approximately 60 inches of total depth. A toilet's depth ranges between 26 and 29 inches. Thirty inches of clearance is recommended at the front of the toilet. For the sink, a 40-inch side-to-side span is also recommended, as are 30 inches of open space in front of the fixture.