Part 1 Conducting Research. Understand what inventions or ideas are eligible for a patent. You can patent your idea if it's a process, a machine, an article of manufacture, a composition of matter, or an improvement of any of these.
Quick Answer. The standard size of a bathtub is 60 inches long, 32 inches wide and 18 inches tall. Standard-sized tubs are designed to fit into an alcove, surrounded by three walls. Alcove tubs are available in a wide variety of materials.
Down the Drain. A standard modern bathtub drain is 1 1/2 inches in diameter -- the width straight across the middle. Rough-in plumbing should be calculated for a 1 1/2-inch pipe. Local building codes vary in requirements regarding the slope and venting method of the drain. Antique bathtubs, such as historic clawfoot tubs, sometimes have slightly smaller drain openings, often 1 3/8 inches in diameter.