Shower Tile Calculator: Square Footage of Walls, Floor, Curb and Niche
A shower is six surfaces, not one rectangle, so its square footage is easy to underestimate. This adds up the walls, the pan, the curb and the niche, then tells you the tile and the waterproofing that go over all of it.
Your shower
Your square footage and what to buy
- Total square footage to tile — sq ftWalls, pan, curb and niche added together.
- Tiles to buy — tiles
- Boxes to buy — boxesRounded up. Buy them in one trip so they share a dye lot.
- — walls — sq ft
- — pan — sq ft
- — curb — sq ft
- — niche — sq ft
- Waterproofing to cover — sq ftMembrane or liquid, plus 15% for overlaps at corners and seams.
- Weight of the order — lbWhat actually arrives, counting whole boxes. Worth knowing before you promise to fetch it yourself.
- Weight of one box — lbThe number that decides whether this is a car trip or a delivery.
A shower is six surfaces
The reason shower estimates come out short is that people price the walls and forget everything else. A typical alcove shower has three walls, a pan, a curb with three faces of its own, and usually a niche made of five small panels. That is a lot of separate rectangles, and every one of them is bounded by cut edges.
This calculator adds them up individually so you can see where the area is going, and it carries a higher waste allowance than a floor because a shower is essentially all perimeter.
Measuring each part's square footage
Walls. Measure the back wall width and the depth of the side walls, then decide how high the tile goes. It has to run above the shower head; stopping partway up the wall leaves a ledge that collects dust and reads as a budget decision. Running to the ceiling costs two or three extra courses and looks intentional.
The pan. If it is getting tiled — mud bed or a foam pan — it is the back width times the side depth. A pre-formed acrylic or solid-surface base is not tiled, so leave the box unticked.
The curb. This is where people go wrong. The curb is not its footprint: it is a strip that runs up the outside face, across the top and down the inside face. Put a tape over it and read the total. Fourteen inches is common for a curb built on a doubled 2×4, but yours is whatever yours is. A curbless shower gets zero here.
The niche. A niche is its back panel plus four returns. A 14 by 20 inch niche with 3½ inch sides is only about 3.5 square feet, which sounds trivial until you realize it is eight or nine small pieces, several of them mitred, in the most closely examined spot in the room.
Why the waste allowance starts at 15%
On a floor, the middle of the room is full tiles and only the perimeter gets cut. In a shower there is barely any middle. Every tile meets a corner, the curb, the niche, the valve, the shower arm, or the sloped pan. The offcuts are mostly narrow strips and wedges you cannot use anywhere else.
Fifteen per cent for a straight layout in a shower is not generous — it is the floor. Add more if the tile is large format, because a broken 12 × 24 costs you a lot more area than a broken subway tile, and large panels are exactly what people break while cutting a valve hole.
Waterproofing is a separate material
Tile is not waterproof and neither is grout. The waterproofing sits behind the tile, and it is the layer that decides whether the wall behind the shower is still there in ten years.
The calculator gives you the tiled area plus 15% for overlaps, because sheet membranes have to lap at every seam and corner, and liquid membranes need multiple coats with reinforcing fabric at the changes of plane. That 15% is a planning figure — the actual overlap dimension is in the manufacturer's instructions and it is not a suggestion.
Two things worth knowing before you buy:
- Membrane and mortar have to be compatible. Several sheet membranes require unmodified thinset, because the membrane is impervious and a modified mortar cannot cure properly trapped between two non-porous surfaces. Read the membrane instructions and buy the mortar they name.
- The corners and the changes of plane are the whole job. Flat wall is easy. The inside corners, the curb-to-pan transition and the four corners of the niche are where showers leak, and they are where the pre-formed corners and reinforcing bands earn their money.
The niche is worth planning around
Nothing in a shower gets looked at as hard as the niche, and nothing exposes bad planning faster.
Set its width so that it lands on full tiles, or on a symmetric pair of cuts. Set its height so a horizontal grout line runs into it cleanly. If the field is a running bond, decide whether the niche interior follows the same offset or resets to a stack — both look fine, but drifting between them looks like an accident.
Do this before you tile the field, not after, because the niche position is fixed by framing and waterproofing long before the first tile goes up. It is the one part of a shower where an hour with a tape and a pencil visibly changes the result.
Where the tile height should land
Common heights, and what they signal:
| Height | Where it works |
|---|---|
| 6 ft above the floor | Bath–shower combos; the practical minimum, and it looks like a minimum |
| Above the shower head, ~7 ft | The usual compromise; leaves a painted band above |
| Full height to the ceiling | Best-looking, easiest to clean, no ledge; costs a few extra courses |
If there is a steam unit, the ceiling gets tiled and waterproofed as well — add its area as another wall's worth.
A worked example
An alcove shower 5 feet wide and 3 feet deep, tiled to 7 feet, with a tiled pan, a 3 foot curb measuring 14 inches over the top, and a 14 by 20 inch niche 3½ inches deep. Tile is 12 × 24 porcelain, 1/16 inch joints, running bond.
- Walls: (5 + 3 + 3) × 7 = 77 sq ft
- Pan: 5 × 3 = 15 sq ft
- Curb: 3 × (14 ÷ 12) = 3.5 sq ft
- Niche: (14 × 20 + 2 × 3.5 × 34) ÷ 144 = 3.6 sq ft
- Total tiled area: 99.1 sq ft
- Module: 12.0625 × 24.0625 ÷ 144 = 2.016 sq ft, so bare coverage is 50 tiles
- With an 18% running-bond shower allowance: 59 tiles, or 8 boxes at 15.5 sq ft
- Waterproofing: 99.1 × 1.15 = 114 sq ft
Note that the niche is 3.6 square feet — under 4% of the job — and will take a disproportionate share of the day.
What this calculator assumes
- The niche is figured as its back panel plus all four returns. Small niches produce a lot of small cuts, which is part of why the waste allowances here are higher than for a floor.
- Curb girth is the distance a tape travels over the curb: up the outside face, across the top and down the inside face. Measuring it beats assuming it.
- Waterproofing is the tiled wall area plus the pan, curb and niche, plus 15% for the overlaps a membrane needs at every corner and seam.
- Shower waste allowances start at 15% rather than 10%. Almost every tile in a shower meets a corner, a curb, a niche or a valve.
- This does not size the pan itself, the pre-slope, or the drain assembly.
- The preset sizes fill in a typical tile so you are not starting from a blank form. The dimensions are the nominal format and are reliable; the thickness is typical for that format rather than a specification, and the box coverage is a middle-of-the-road figure, not a standard.
- Box coverage is the one number you should check against your own box. Surveying current 12 x 24 porcelain listings at a large US retailer turned up cases from 11.64 to 16 square feet — a 37% spread for the same nominal tile. 3 x 6 subway is far more consistent, with 12.5 square feet dominating, and 6 x 24 plank clusters tightly around 14.55. Squares vary the most.
- Weight is worked out as thickness x density x area, using nominal densities of 150 lb per cubic foot for porcelain, 125 for ceramic and 165 for natural stone. It counts the tile only: no mortar, no backer board, no pallet. The order weight is based on whole boxes, because whole boxes are what turn up.
Common questions
How high should the tile go?
It has to run above the shower head, and stopping at some arbitrary line below the ceiling gives you a dust ledge and an obvious budget decision on display. Running to the ceiling costs a couple of extra courses and looks deliberate. In a bath–shower combo, 6 feet above the floor is the common minimum.
Why is the waste allowance higher than for a floor?
Because waste follows cut edges, and a shower is nearly all edges: three internal corners, a curb, a niche, a valve, a shower arm, and a floor that slopes to a drain. A 15% allowance on a shower is not generous, it is realistic.
Does the niche really need its own numbers?
Yes. A 14 by 20 inch niche with 3½ inch returns is only about 3.5 square feet, but that area is made of eight or nine small pieces, several mitred, and every one of them is a chance to break a tile. Budget the area, then budget the patience.
What about the ceiling?
If the shower has a steam unit, the ceiling gets tiled and waterproofed too — add it as another wall's worth of area. For a standard shower, most people paint it.
Where these numbers come from
- Waterproofing overlap allowance reflects the seam and corner treatment that sheet and liquid membrane manufacturers require; the specific overlap dimension is in their instructions.
- Waste allowances are typical trade figures for shower work, raised above floor allowances because of cut density.
- Preset box coverages were taken from the spread of real product listings rather than from any single manufacturer, and are declared as typical rather than standard. Your own box is the authority.
- Tile densities for the weight figure are the usual nominal values for each material: roughly 150 lb/cu ft for porcelain, 125 for ceramic and 165 for natural stone.
Last checked 2026-08-20.