A 60 × 36 in alcove shower tiled to 8 ft has 88 sq ft of wall, and with a 12 × 24 in niche and a 4 in curb that grows to 95 sq ft: 52 tiles of 12 × 24 in with 10% extra. The 15 sq ft floor takes 17 mosaic sheets. Walls and floor are counted separately because they almost always use different tile.
How the shower tile is calculated
The walls are rectangles: back wall width × tile height, plus each side wall's depth × tile height. A recessed niche does not remove tile: its back replaces the piece you cut out of the wall, and its four inside faces (the returns) add 2 × (niche width + niche height) × niche depth. A curb adds its top and both faces along the shower width. A bench adds its top to the floor tile and its front to the wall tile.
wall tile area = width × height + 2 × depth × height + niche returns + curb + bench front
tiles = area ÷ ((tile width + joint) × (tile length + joint)) × (1 + waste %), rounded up
Worked example
The calculator's defaults: a 60 × 36 in shower, walls tiled to 96 in, 12 × 24 in wall tile at ⅛ in joints, a 12 × 24 × 3½ in niche, a curb 4 in tall and 4½ in wide, 2 in mosaic on the floor.
- Back wall: 5 ft × 8 ft = 40 sq ft. Side walls: 2 × 3 ft × 8 ft = 48 sq ft.
- Niche returns: 2 × (12 + 24) × 3.5 = 252 sq in, 1.75 sq ft.
- Curb: 60 in × (4.5 + 2 × 4) in = 750 sq in, 5.21 sq ft.
- Wall tile: 94.96 sq ft ÷ 2.031 sq ft per tile × 1.10 = 52 tiles.
- Floor: 15 sq ft of 12 × 12 in mosaic sheets = 17 sheets.
- Cement board for walls and niche: 89.75 sq ft in 3 × 5 ft sheets = 7 sheets.
- Waterproofing for walls, floor, curb and niche: 110 sq ft = 2 gallons of RedGard.
- Grout: 9.4 lb for walls and floor, one 10 lb bag. Thinset: 4 bags of large-tile mortar for the walls, 1 bag for the floor.
The elevation drawing unfolds the three walls side by side with each tile in place, so you can see where the cut rows land and how the niche sits in the pattern. A niche sized to whole tile modules, with its top and sill on grout lines, saves the fiddliest cuts in the shower.
Wall height and the shower floor slope
The International Residential Code asks for a nonabsorbent wall surface at least 6 ft above the floor in showers and tub surrounds (R307.2). Most people tile to the ceiling anyway, since a cut row at 6 ft looks unfinished.
The floor must fall to the drain at no less than ¼ in and no more than ½ in per foot (IRC P2709.1). With a center drain the longest run is half the larger dimension, so this 60 in wide pan rises 30 in × ¼ in per ft = ⅝ in at the side walls. A linear drain along the back wall turns the floor into one plane falling over the full 36 in depth, which lets you use large tile on the floor because nothing has to bend around a cone. The same section limits the curb to between 2 and 9 in above the drain, measured from the top of the curb; the default curb stands 4⅜ in above the drain (4 in plus the ⅜ in the floor rises to the curb).
Mosaic or large tile on the floor
Small tile follows a four-way slope toward a center drain; each sheet flexes into the shape. The joints also give bare feet grip. A 12 × 24 in tile on a center-drain floor needs cuts along every valley. With a linear drain, large tile works well: pick the size in the floor tile field and the grout and thinset follow.
Backer board, foam board and waterproofing
Cement board does not stop water, it only survives it: a liquid membrane goes over walls, floor, curb and niche. RedGard's data sheet gives 55 sq ft per gallon for a waterproof membrane in two coats, or 192 sq ft per 3.5 gallon pail; wall board comes in 3 × 5 ft and 32 in × 5 ft sheets (USG Durock sizes). Foam board such as KERDI-BOARD is waterproof itself, so the calculator only counts membrane for the floor and curb and you seal the board seams with the maker's band.
The rest of the bathroom
For the bathroom floor outside the shower and any wainscot, add them as surfaces in the tile calculator. The grout calculator shows brand coverage for the grout you picked, and the thinset calculator explains why the walls get a ½ in notch and the mosaic floor a ¼ in one. Seal the corners and the tub or pan edge with silicone rather than grout; the caulk calculator counts the tubes. For the budget of the whole room, the bathroom remodel cost calculator puts a price on it.