Calculating Tile for a Small Bathroom, Fixture by Fixture
I was kneeling on the subfloor of our hall bathroom, tape measure hooked over the door threshold, trying to settle a slippery question: what counts as floor? The walls taped out at 5 feet by 8 feet — 40 square feet on paper. But a tub claimed one whole end of the room, a vanity hugged the long wall, and a toilet flange stared up from the middle of everything. Tile costs real money even in cheap ceramic, and I had no intention of paying for 40 square feet when maybe 28 of them were visible floor.
That instinct was half right. The wrong half sent me back to the store mid-install, and the receipt from that second trip taught me more about small-bathroom tile math than any formula has. What follows is the actual room, the actual order, and the exact place it all went sideways.
Three Fixtures, Three Different Answers
The tub gets subtracted. Mine is a standard 60-by-30-inch alcove tub spanning the 5-foot end of the room, which works out to a 12.5-square-foot footprint. Tile doesn’t go under an alcove tub — the tub sits on the subfloor and the tile dies into the apron. Pulling 12.5 from 40 left me a tiled field of 27.5 square feet, a clean 5-foot by 5.5-foot rectangle.
I tiled under the vanity, and I’d do it again. The cabinet is 24 inches wide and 21 inches deep — 3.5 square feet, four tiles at most. Skipping it would have saved me about six dollars; replacing that vanity someday with a pedestal sink or a narrower cabinet would leave a vanity-shaped hole of bare subfloor. Four tiles is cheap insurance.
Nobody should subtract the toilet. It comes off, the tile runs underneath right up to the flange, and it goes back on. Budget the full area as if the toilet didn’t exist, then budget extra patience for the flange cut, which is the nastiest cut in the room. One scope note: whether your flange sits at the right height after the new floor goes down is a plumbing question — well outside what a tile count can tell you. Mine was fine. Yours is between you and your flange.
The Order I Placed
My tile was a 12-by-12 ceramic at $1.59 a square foot, sold by the piece — convenient, because each tile is exactly one square foot. I ran the standard math: 27.5 square feet times 1.10 for waste is 30.25, round up to 31 tiles. Total: $49.29.
For comparison, ordering for the whole 40-square-foot room at the same 10 percent would have meant 44 tiles and $69.96. By subtracting the tub I’d shaved 13 tiles — $20.67 — off the order, and I drove home feeling like I’d beaten the system.
Where the Tub Edge Took It Back
The field laid out as five tiles across and five full rows deep from the door wall — 25 field tiles, two of them notched around the flange — then one final row along the tub that needed to be ripped down to 6 inches. (Nominal 12-inch ceramic runs a hair under 12, which spared me side cuts I had no right to dodge.) Five cut tiles, five 6-inch offcut strips on the scrap pile: 2.5 square feet of waste before anything went wrong, and the honest kind, because every floor has a cut row somewhere.
Then things went wrong. I cut all five tub-row tiles at an even 6 inches, dry-fit them, and discovered the tub apron wandered three-eighths of an inch over its 5-foot run. The gap at one end was closer to 5⅝ inches, and a snap cutter cannot shave three-eighths off a ceramic tile — the sliver crumbles instead of snapping. All five pieces went in the trash, and five fresh tiles got scribed to the apron one at a time. The flange was its own small war: I cracked three tiles trying to nibble the curve before the fourth and fifth attempts survived. Add one door-jamb notch I cut mirror-backwards and one tile I chipped by stepping on it, and the tally came to 40 tiles consumed — 25 field tiles, 5 spoiled straight cuts, 5 scribed replacements, 3 flange casualties, 1 backwards notch, 1 boot print.
I’d bought 31. The second trip was 9 tiles and $14.31, bringing the total to $63.60 for a 27.5-square-foot floor. Sweeping up that night, I did the dispiriting arithmetic: 40 square feet of tile consumed minus 27.5 covered equals 12.5 square feet of scrap. Exactly the footprint of the tub I’d been so proud to subtract. Net savings versus the lazy whole-room order: $6.36, one extra drive, and zero spare tiles left over for future repairs.
Why Small Rooms Carry the Highest Waste
Waste lives at edges, and a small bathroom is nearly all edge. My 5-by-8 room has 26 linear feet of perimeter wrapped around 40 square feet — 0.65 feet of cut line per square foot of floor. A 12-by-12 bedroom has 48 feet around 144 square feet, half the ratio at 0.33. Subtracting the tub made my actual field worse, not better: about 21 feet of edge around 27.5 square feet, plus a flange in the middle. Three-quarters of a foot of cut line for every square foot of floor.
The waste numbers I use everywhere on this site are 10 percent for a straight lay, 15 for diagonal, 20 for herringbone, with complicated rooms taking the high end of whatever range applies. A small bathroom is a complicated room by definition. Treat a straight lay in a 5-by-8 bath as a 15 percent job, and give a diagonal lay the full 20. Even the legitimate, nothing-went-wrong cut loss in my room — the 2.5 square feet of tub-row strips, one realistic flange casualty, one miscut — comes to about 4.5 square feet, and 4.5 over 27.5 is 16 percent.
No waste percentage covers redoing an entire row, though. At 15 percent I’d have bought 32 tiles and still come up 8 short. The percentage buys normal cut loss; botches ride on top of it. Your defenses are practical rather than mathematical: dry-fit the tub row before setting it, scribe to the apron instead of trusting it to be straight, buy a tile the store actually stocks so a second trip is possible, and keep the receipt.
The Numbers I’d Run Today
For a 5-by-8 bathroom with an alcove tub, the recipe is short. Measure the gross floor, subtract the tub footprint (12.5 square feet for a standard 60-by-30), tile under the vanity, ignore the toilet. Apply 15 percent: 27.5 × 1.15 = 31.6, round up to 32 tiles. Then buy two or three past that on purpose, because spares in the garage beat hunting a discontinued dye lot every time. If your tile comes boxed instead of by the piece, divide by the coverage printed on the box and round up — box counts vary too much to guess at.
Run your own room through the flooring calculator and pick the Diagonal (+15% waste) option — the tool ties waste to the layout pattern, and for a small, chopped-up bathroom that 15 percent is the right buffer even when the tile runs straight. And if you want the longer argument behind those percentages, the flooring waste percentages guide walks through where each number comes from. Subtracting the tub is still the right call. Just go in knowing the edges of a small room will claw a chunk of that savings right back.