Standard Shower Sizes and Their Square Footage

Everyone answers this question in inches

Search for shower sizes and you get inches. 32 by 32, 36 by 36, 60 by 30, a note that walk-ins are getting bigger, and a photograph. All of it accurate, none of it the number you asked for.

Square footage is a different question, and it has two answers rather than one. There is the floor — the pan, the thing the size on the box describes — and there is the wall. The tables above give both, because the two are nothing like each other.

A 36 by 36 alcove shower has 9 square feet of floor and 54 square feet of wall at the code minimum height. Tile it to an eight foot ceiling and the wall is 72. The floor is barely a tenth of the job.

Count your walls before you do anything else

There are two charts above because there are two showers, and the difference between them is larger than the difference between any two sizes on the list.

An alcove shower is a slot with three tiled walls and glass across the open face. A corner shower has two tiled walls and glass on the other two sides. Same floor, same size on the box, and roughly a third less tile in the corner version — a 36 by 36 is 54 square feet as an alcove and 36 as a corner.

Square showers, which is most of the small end of the list, are usually corners. Long rectangles are usually alcoves. But "usually" is not a measurement, so look at your own bathroom and count the walls that will actually take tile.

The wall is the shower, as far as your order is concerned

That ratio is the most useful thing on this page, so it has its own column in both charts. In an alcove:

• 30 by 30 — 7.2 square feet of wall per square foot of floor
• 36 by 36 — 6.0
• 60 by 30 — 4.8
• 72 by 42 — 3.7

In a corner the numbers are lower — 4.8 down to 2.7 — but they fall in exactly the same way.

It runs backwards from what people expect. The smaller the shower, the worse the ratio gets. A shower is a box with one side missing, and as the box shrinks, its walls shrink more slowly than its floor does — the floor falls with the square of the dimensions, the walls only with the perimeter.

This is the arithmetic behind a complaint every remodeler hears: why is a tiny bathroom not much cheaper than a big one? Because you are buying wall, not floor, and the wall barely moved. Add that the valve, the pan, the waterproofing membrane and the tiler's day are all effectively fixed, and the small job comes out at nearly the same price with a fraction of the result.

If you are choosing between a 36 by 36 and a 48 by 36 to save money, the honest number is 6 square feet of extra tile. That is often less than the waste allowance.

Where the numbers stop being conventions

Everything in the first chart is what the market sells. Nothing about 36 by 36 is written down anywhere — it is just a size that manufacturers settled on and now stock.

The second chart is different. Those figures are code, and they are the only ones on the page that a plan reviewer will hold you to.

The one to know is 900 square inches. Under IRC section P2708.1 a shower compartment needs at least that much interior area, with no dimension under 30 inches. Nine hundred square inches is 6.25 square feet, and 30 by 30 hits it exactly — which is why 30 by 30 is the smallest shower you will find, and why it feels like a phone booth.

There is a second door. The same section allows a minimum dimension of 25 inches provided the compartment has at least 1,300 square inches, or 9.03 square feet. That is the exception used when a long narrow shower is the only way a bathroom works.

Two details in that clause get quoted wrong constantly:

1. It is measured on the finished interior. Not the framing, not the pan's nominal size. After backer board, membrane, thinset and tile, you can lose the better part of an inch on each wall.
2. The area is measured excluding the fittings — valves, shower heads, soap dishes, grab bars — and it has to hold that clear area all the way up to 70 inches above the drain outlet. A shower that meets 900 square inches at the threshold and then narrows above it does not comply.

So a base advertised as 30 by 30 is not comfortably legal. It is exactly at the limit before anything is built on top of it. Design to that number and you are relying on the tile being thin.

How high you tile is a bigger decision than it looks

The code minimum, from IRC R307.2, is a nonabsorbent wall surface 72 inches above the floor.

Notice what that says. Above the floor. Not above the tub rim, not above the pan.

That distinction is worth real money on a tub-shower, and it cuts both ways. A standard five foot cast iron alcove tub has its rim at 14 and a half inches, so satisfying the code means about 57 and a half inches of actual tile above the tub, not 72 — you do not tile the strip the tub is standing in front of. The tub chart above is measured from the rim for exactly that reason. Work from the 72 and you will buy about a quarter more tile than the job needs.

It also explains something you have seen in every older bathroom: a tiled band that stops at an apparently arbitrary height with paint above it. It was not arbitrary. It was the minimum.

The last chart shows what the height decision costs. On a 60 by 30 alcove, going from the 72 inch minimum to the ceiling at 96 inches takes the order from 60 square feet to 80 — a third more tile, for a choice most people make by looking at a photograph.

Three heights are worth thinking about:

• 72 inches. Legal. Looks unfinished in a modern bathroom, and leaves a horizontal joint where the tile stops that has to be sealed and will eventually be the thing that fails.
• Just above the shower head, usually 78 to 84 inches. The pragmatic choice, and it protects the surface that actually gets wet.
• To the ceiling. More tile, no top edge to detail, and the only version that looks intentional in a small room.

What these figures leave out

They are floor and wall only. Three things are not in them, and all three are ordered late and short:

• The ceiling. A tiled shower ceiling adds the floor area back again — 9 square feet on a 36 by 36. It is common in steam showers and increasingly common everywhere else.
• The curb. Its top, its outer face and its inner face wrap to about 14 to 18 inches of surface, so multiply that by your opening width: 3.5 to 4.5 square feet across a 36 inch opening, 5.8 to 7.5 across a 60 inch one. Curbs eat tile disproportionately, because almost every piece on them is a cut.
• A niche or a bench. Small in area, large in cuts and in trim.

And a wet room with no enclosure at all is outside both charts. There is no clean formula for one — measure the walls you intend to tile and use the height columns.

Turning this into an order

The square footage on this page is the surface to be covered. It is not the tile to buy, and the gap between the two is bigger on a shower than almost anywhere else, because a shower is nearly all edges: every wall meets another wall, the ceiling, the pan or a curb, and nearly every tile in the room gets cut somewhere.

The route from here is short. Take the wall figure for your size and tile height, add the floor if you are tiling it, add the ceiling and curb if they apply, and then run it through a waste allowance and a box count — a percentage is not a purchase, and tile is sold in boxes.

The shower tile calculator does the whole path from dimensions, and the tile waste factor page explains why the box count on a small job overshoots your percentage by so much.