Bathroom tiles cannot be as large as those on the floors of living room and bedroom. Every room or space has specific purposes and those utilities will determine the necessary attributes of the flooring material chosen. Bathroom is a wet room. The needs are naturally different. You can always opt for standard sizes of tiles for the bathroom floor and walls, but the precise wet area should have smaller tiles. It is best to go for miniature tiles or at least half the standard foot by foot size opted for in other rooms. A two square foot tile is often a nonstarter for a bathroom.
There are many reasons why bathroom tiles must be smaller, but one serves as an enough rationale. Wet rooms, be it bathrooms or utility areas, will have a certain gradient. There must be a gentle slope to facilitate gravity working its magic to direct the flow of water as naturally as possible. There should not be any pooling of water in any part of the bathroom. The transient pooling near the drain does not make much of a difference if the pipe is not clogged. The gradient or slope will have to be factored in during the installation of the floor tiles. Smaller tiles are more compatible with a slope than larger tiles.
You must not think that larger tiles cannot be installed on a slope. It is just simpler, easier and more effective to install smaller tiles impeccably on a sloping surface. You will notice that the smaller tiles will be more compatible whenever the slope becomes obvious near the drain. Since smaller tiles take up less space and a more of them are used, it is also more affordable to carve out the necessary shapes of those tiles as and where required.