How to Calculate Tile for a Shower (Step-by-Step)

A shower is the hardest surface in the house to tile, and it is the one most calculators handle worst. It has a floor that slopes, walls that stop at a dam, a niche cut into framing, and often a different tile from the rest of the room. This guide walks through the whole calculation, surface by surface, with real numbers.

The short version: measure each flat surface separately, add them, divide by one tile’s area, then add waste. Everything below is that sentence with the details that actually change the answer.

Step 1 — Break the shower into flat surfaces

Count what you are actually tiling:

• The pan (floor) — the sloped base, usually a small mosaic or 2×2 in tile.
• Three walls — two side walls and a back wall in an alcove; four or more in a walk-in.
• The ceiling — only if it is tiled, which is common over a rainfall head.
• The niche back and shelves — one flat rectangle per niche, plus the four returns if you are not using a trim piece.
• The bench or seat top — a rectangle, plus the front face.

Every one of those gets its own line. That is not bookkeeping for its own sake: the pan needs 20–25% waste while a straight back wall needs 10–12%, and mixing them into one number gives you a buffer that is wrong in both directions.

Step 2 — Measure each surface

Measure at three points — top, middle and bottom — and use the largest number. Old studs bow and shower pans are rarely square.

For a standard 3 ft × 3 ft alcove with an 8 ft ceiling:

Deduct only big openings — a full glass door, a window over about 10 sq ft. Leave niches, valves, the shower head arm and the drain flange in the count: each one eats a cut tile anyway, and pulling it out of the total double-charges you for the cuts around it.

Step 3 — Account for the niche and bench

A niche is 12×24 in of missing wall tile, but it adds five surfaces worth of cuts: the back, and the four returns. The usual practice is to leave the niche area in your wall total and let the extra waste percentage absorb the returns. If the niche uses a different tile or a mosaic, run it as its own line so the harder cuts get their own allowance.

Same logic for a bench: the top is a plain rectangle, but the front face and the joint where it meets the wall each need a clean cut. Give a bench 20% waste on its own lines.

Step 4 — Divide by the tile

Take the total area and divide by the area of one tile.

A 4×12 in subway tile is 0.333 sq ft. Your 81 sq ft of straight walls (72 sq ft) becomes:

72 ÷ 0.333 = 216 tiles

A 2×2 in mosaic sheet usually covers 1 sq ft, so the 9 sq ft pan is about 9 sheets.

Watch the units. If you measured in metres, the tile dimensions must be in metres too — 300×300 mm is 0.3 m × 0.3 m = 0.09 sq m, not 0.9.

Step 5 — Add waste by surface

This is where showers and floors diverge. Perimeter cuts, the slope on the pan and the constant miters around a niche all push the number up.

So the 216 subway tiles above become 216 × 1.15 = 249 tiles, and the pan sheets become 9 × 1.25 ≈ 12.

Step 6 — Convert to boxes

Tiles come in boxes and you cannot buy a fraction of one. If the subway tile is 8 pieces per box, 249 tiles is 31.1 boxes — order 32.

Order one extra box on top if the tile is discontinued or from a small run. Dye lots drift between batches and an unrepairable shower wall in two years costs far more than a box sitting in a cupboard now.

Common mistakes

• Treating the shower as one rectangle. The pan and the walls want different waste, different tile and different grout.
• Deducting the niche. You remove the area, then still have to cut around it — you pay twice.
• Forgetting the dam and the threshold. That thin strip at the door needs its own cut and is easy to miss.
• Ordering exactly what the math says. Rounding down to save one box is the most common reason a job stalls mid-wall.

Worked example, end to end

An alcove shower, subway walls in offset pattern, mosaic pan:

• Walls: 72 sq ft ÷ 0.333 sq ft = 216 tiles × 1.15 = 249 tiles → 32 boxes of 8
• Pan: 9 sq ft ÷ 1 sq ft = 9 sheets × 1.25 = 12 sheets
• Grout: roughly 3 kg for the walls, 1.5 kg for the pan — the calculator works this out from the tile size and gap you enter

Enter the three walls and the pan as separate sections and the tool keeps each waste rule intact while returning one combined tile, box, grout and cost total.

Use the shower tile calculator to run your own numbers, or read how to find your shower’s square footage first if you have not measured yet.