Understanding your result
The headline is the boxes of wall tile. The stats add the wall tile area, the number of wall tiles, the floor mosaic sheets and the trim pieces, and the breakdown lists each part of the shower in turn: the walls, the niche returns, the curb, the wall tiles and boxes, the floor and its boxes, and the trim length and pieces.
The wall tile area is more than the walls. The niche adds its returns (the tile going into the recess), and the curb adds its top and two faces. These are small areas, but together they are a box, and they are the pieces that get forgotten. The wall tiles to order then follows the same path as the wall tile calculator: tile with its joint, tiles before waste, the layout’s allowance, whole boxes.
The floor is counted separately because it is a different tile. Mosaic sheets are 1 sq ft each, with 10% for the cuts around the drain and along the walls. The trim covers the two exposed vertical edges of the shower opening, the perimeter of the niche and both long edges of the curb, in pieces of the length you entered plus 10% for mitres. Under the result the calculator reminds you of what it does not count: the board, waterproofing, thinset and grout, which the cement board calculator and the grout calculator work out from the same areas.
How we calculate this
An alcove shower has three walls (the back and two sides); a corner shower has two (the back and one side), with the other two sides glass or open. The curb is assumed to run the width of the back wall, which is where the opening is in an alcove; if your opening is on a side, enter the side width as the back and vice versa. Tile pitch, tiles per box and the layout allowance work as described on the waste factors page and in the guide to tiling a shower, which walks through a complete shower from board to grout.
The assumptions behind the numbers
| Assumption | Default | Where it comes from |
|---|---|---|
| Shower | 60 × 36 in alcove, tiled 8 ft high | The most common US alcove size (a 60 in tub or shower base); heights of 7 to 8 ft are typical |
| Niche | 12 × 24 in, 3.5 in deep | Prefabricated niches and stud bays: a 2 × 4 wall gives 3.5 in of depth |
| Curb tile | 16 in of tile per foot of curb | A 6 in top with a 4 in inside face above the pan and a 6 in outside face; the TCNA Handbook shower details show a curb of this proportion |
| Wall tile | 12 × 24 in, 1/8 in joint, 16 sq ft boxes | Common bathroom wall tile; manufacturer specification sheets (2025) |
| Floor | 12 × 12 in mosaic sheets, 10 per box, 10% waste | Standard mesh-mounted mosaic packaging; TCNA notes that sloped shower floors take tile of 2 in or smaller unless a single-plane slope is used |
| Trim | 12 in pieces, 10% for mitres | Bullnose and pencil trims are typically 12 in |
Assumptions last reviewed October 7, 2026.
The calculator does not model a bench (add its top and front as a wall of the right size), a half wall, a second niche or a window in the shower. It assumes the floor is a rectangle and the curb a straight line. And it counts tile only: the substrate, waterproofing, setting materials and silicone are separate items. The guide to tile size and grout joints explains why the joint on a shower wall is kept narrow and what that does to the grout quantity.
Two worked examples
A tub surround with a niche
Alcove 5 ft back, 3 ft sides, tiled 8 ft above the tub deck, a 12 × 24 in niche, no curb (it is a tub) and no tiled floor. 12 × 24 tile, 1/8 in joint, straight layout, 16 sq ft boxes at $40.
- Wall area: (5 + 2 × 3) × 8 = 88 sq ft
- Niche returns: 2 × (12 + 24) × 3.5 ÷ 144 = 1.75 sq ft; total 89.8 sq ft
- Tiles before waste: 89.8 ÷ 2.031 = 44.2; with 10%: 49 tiles
- Boxes: 49 ÷ 8 = 6.1, rounded up to 7 boxes, $280
- Trim: 2 × 8 ft of exposed edge + 6 ft of niche perimeter = 22 ft; 264 in ÷ 12 × 1.1 = 24.2, rounded up to 25 pieces
Seven boxes is 56 tiles for a job that needs 49, and the 7 spare are the repair stock. The 25 pieces of bullnose are the surprise on most first shower orders; they are also the piece that most often sells out in the matching colour, so they go on the same order.
A 4 × 4 ft corner walk-in shower
Corner shower, back and side walls 4 ft each, tiled 8 ft high, a 14 × 28 in niche, a tiled curb, a 4 × 4 ft mosaic floor. 12 × 24 wall tile, straight, 16 sq ft boxes; mosaic 10 sheets per box.
- Wall area: (4 + 4) × 8 = 64 sq ft; niche returns 2 × (14 + 28) × 3.5 ÷ 144 = 2.0 sq ft; curb 4 × 16 ÷ 12 = 5.3 sq ft; total 71.4 sq ft
- Wall tiles: 71.4 ÷ 2.031 = 35.1; with 10%: 39 tiles, 5 boxes
- Floor: 4 × 4 = 16 sq ft × 1.1 = 17.6, rounded up to 18 sheets, 2 boxes
- Trim: 2 × 8 + 7 + 2 × 4 = 31 ft; 372 in ÷ 12 × 1.1 = 34.1, rounded up to 35 pieces
The corner shower has two tiled walls and two glass sides, so the wall tile is modest, but the trim is longer than the alcove’s because the curb is edged on both sides. Eighteen sheets of mosaic for 16 sq ft is the 10% for the drain cut and the slope; a square floor with a centre drain is cut on all four sides.
Where to find your inputs
Back and side widths. Measure the finished walls at the level of the tile, not the base. For a tub, the back wall is the tub length and the sides are the tub width to the front edge.
Tile height. From the tub deck or the top of the pan to the top of the tile. Many showers are tiled to 7 ft; to the ceiling is 8 ft or more.
Niche. The size of the prefab niche or the framed opening, and its depth, which in a 2 × 4 wall is 3.5 in.
Floor. The inside dimensions of the pan or the mud bed, wall to wall. A curb is not floor.
Coverage per box. From the wall tile box and the mosaic box; mosaic boxes are usually described by sheets.
Common mistakes
- Counting three walls and nothing else. The niche returns, the curb and the trim are a box and a half on a typical shower.
- Using the wall tile on the floor. A sloped shower floor takes mosaics. Large tile on a shower floor needs a linear drain and a single-plane slope.
- Ordering trim later. Bullnose is made in the same dye lot as the tile. Later batches do not match.
- Forgetting that the curb has three faces. It is 16 in of tile per foot, not 6.
- Half-offsetting large tiles. Keep brick patterns of 12 × 24 to a one-third offset, as the TCNA Handbook says.
- Leaving out the substrate. Cement board, waterproofing, thinset and grout are separate orders; the calculators for each take the areas from this page.
Questions people ask
- How many boxes of tile for a standard shower?
- A 60 × 36 inch alcove shower tiled 8 ft high has 88 sq ft of wall. With a 12 × 24 niche and a tiled curb that becomes about 96 sq ft, which in 12 × 24 tile with 10% waste is 53 tiles and 7 boxes of 8. The 15 sq ft floor takes 17 mosaic sheets, so 2 boxes of 10.
- Does a niche need extra tile?
- The back of the niche replaces the wall tile that was cut out, so it adds nothing. The four returns (top, bottom and two sides) are new area. For a 12 × 24 inch niche 3.5 inches deep they add 2 × (12 + 24) × 3.5 = 252 sq in, about 1.75 sq ft, plus the bullnose or mitres around the opening.
- How much tile does a curb take?
- A curb is tiled on top (about 6 inches wide), on the inside face above the pan (about 4 inches) and on the outside face (about 6 inches), so roughly 16 inches of tile per foot of curb. A 5 ft curb is about 6.7 sq ft, plus trim along both long edges.
- Why is the shower floor counted in mosaic sheets?
- Because the floor slopes to the drain at about 1/4 inch per foot in every direction, and only small tiles can follow a surface that is not flat. Mosaics of 2 inches or less, on 12 × 12 inch mesh sheets, are the standard; large tiles need a linear drain and a single-plane slope.
- What waste should I use in a shower?
- 10% for a straight or brick layout of wall tile and 10% on the mosaic floor, which the calculator applies automatically. A shower has more cuts per square foot than a plain wall, so if the walls have plumbing on more than one side or the tile is a complicated pattern, choose custom and use 15%.
- What else do I need that the calculator does not count?
- Cement board or foam board for the walls, the waterproofing membrane or liquid, thinset for walls and floor, grout, silicone for the changes of plane, and the drain assembly. The cement board, thinset and grout calculators on this site take the same areas.