I'm sorry this is an image from Houzz but to give you an idea. However, you can plot on a graph paper the walls and doors of your bathroom. Then cut out other bits of paper to scale to represent the dimensions of the tub, toilet and vanity you have in mind. Now move them around to fit. It is really the best way to work out the ideal layout for your bathroom. Hope this helps

With white fixtures, keep your floors and all tile white or a stone that is mostly white. You can paint the walls above the wainscot (which might be glossy painted wood or beadboard, or you might employ a cabinet for the sink that was painted a very soft sky blue. One narrow trim piece of tile running through the white tile might be the same tone of sky blue. Then, add blue linens / towels / etc. [houzz=] Now, consider what other colors are in your home and select one that is clear and soft and lovely with white. You might use that color instead of sky blue. I used sky blue because it is the color of water and therefore always appropriate in the bath, but you can make the bath flow with the colors you have or plan to have in your home. If this was a master bathroom instead of a common or guest bath, I would shift the choices of stone and tile from white plus white to a lovely off-white, cream, or almond tone - like travertine. Use a neutral like chocolate on the cabinet and add color only with linens and perhaps some art on the wall. [houzz=]

I suggest you follow the step-by-step guide for creating storage cabinets under the bathroom sink. Take proper measurements - Measure the available available space in height, width and height. Cut Plywood to size - With a circular saw and framing square, cut all the required pieces out. You can use a sliding compound saw as an alternative. Attach the base and sides - Start assembling the sink cabinets by placing the bottom piece of plywood sheet on a flat surface. Attach the back and top boards - Place the plywood sheet for the top part of the cabinet and attach wood screws to connect it to both the sides. Turn the back faces of the cabinet upwards. Keep the back piece over the structure and fix it into place with wood screws. Attach shelves - Place the cabinet in an upright position to install the shelves. Slide a shelf into the structure so it is flush against the back. Attach door - Keep both hinges of the door on the same side of the plywood sheet. Drill them using wood screws into place. Now keep the door over the cabinet structure, extend the hinges to one of the side panels and fix them to make them secure. Fix a hasp closure on the other side of the door, placing it in the center of the hinges.

This is the plan I m referring to. plot is South facing and it's 186.6 sq yards in size