Arriving at just the right size to design your bathroom can be a challenging task. The bigger your bathroom is, the more the cost of construction and maintenance. And if it is too small, it will be cramped and difficult to use. For this purpose, there are certain standards that give you a basic guideline from which you can develop bathroom plans, adjusting sizes according to the clients' needs.
Determine the various zones you would need in your bathroom, and the areas each would require. Common zones include the Shower/Bathtub area, the toilet area, the sink, and the storage area. Apart from these, you would need to determine whether you require any additional space, like perhaps for the washer/dryer.2
Calculate the area required for the bathtub. Add the area occupied by the tub or the shower with the required clearance space that would enable you to access it. A standard bathtub would be 30 inches by 60 inches, while more luxurious bathtubs may be up to 72 inches long. A 34-inch square is the minimum size required for a shower. A shower area that is 36 inches wide and 42 inches long is a more comfortable option. Allow for a width of 30 inches of clearance space in front of the shower/bathtub.3
Measure the area that would be occupied by the toilet. The size of the toilet is normally around 18 inches wide and 30 inches long. Check with your product brochures if you are opting for a larger toilet. Adequate clearance space at the toilet is 20 inches in front and around 15 inches on either side. Add the toilet area with the clearance area to arrive at the total space covered by this zone.4
Decide on the type of sink you are going to use in your bathroom. Sink sizes vary greatly--a single counter sink can be from 26 inches by 22 inches up to 48 inches by 24 inches, or for a two person sink with more counter space, up to 65 inches. The sink area requires at least 30 inches of clearance in front of the sink. Add these areas to determine the total area occupied by the sink.5
Calculate the amount of storage required for your household. It could be as minimum as a cupboard under or alongside the sink, or it could be as spacious as a separate laundry/medicine closet. Estimate the total amount of storage area your family would need and make a note of the value.6
Write the calculations of the area required by each zone of your bathroom down on your graph paper and add them all to get the estimated area that your bathroom will occupy. Now design your own bathroom on your graph paper with each square equaling 1 square foot and using your calculations as a guide.7
Keep in mind that according to the the second edition of the "Time-Saver Standards for Building Types," edited by Joseph De Chiara and John Callender, an average area required for a conventional 3-fixture bath (Tub, sink and toilet) is 40 square feet. This, however, will vary according to individual requirements, with most bathrooms being around 48 square feet, 8 feet in length and 6 feet in width.