What a bathroom takes, box by box and bag by bag.
Floor to ceiling tile, and suddenly it is a hotel. Type your own measurements over the ones already in the fields and every count below moves while you type.
A bathroom is 4 jobs wearing one word. Switch between them on the strip above and your measurements follow you across, because it is the same room every time.
The smallest room, and the worst place to round
A bathroom is the room where a rounding rule stops being a rounding rule and starts being the price. Everything here is bought in boxes and bags sized for rooms four times larger, so the leftover is not a rounding error, it is a share of the job.
Look at the eight by five bathroom this page opens with, at an eight foot ceiling.
- Floor tile. Eight by five is 40 square feet. Ten percent for cuts makes 44, and at the 15 square feet per box this page starts you at, that is 2.93, so three boxes. Three boxes is 45 square feet to cover 40.
- Thin-set. One 50 pound bag. CUSTOM Building Products publishes 85 to 95 square feet per bag with a quarter inch square notch trowel, so a 40 square foot floor does not come close to finishing one, and there is no half bag to buy.
- Paint. Two times eight plus five, times eight, is 208 square feet, less the 40 square feet of door and window assumed until you change it, so 168. Two coats is 336 square feet, which is one gallon at both ends of the published 350 to 400 per gallon range.
- Drywall. Walls plus ceiling is 208 square feet, 229 with ten percent for cuts, and at 32 square feet per four by eight panel that is eight sheets. Which is four bundles exactly, since USG packs two panels to a bundle.
Now do the honest reading of that. Three boxes of tile for a 40 square foot floor means you bought 45 to install 40, and one full bag of mortar rated for at least 85. On a living room floor the same rules cost you a few percent. Here they are most of the difference between the number you expect and the number at the register, and no amount of careful measuring removes them, because the store sells what the store sells.
Floor to ceiling tile is a different rectangle
The look people come to a bathroom for is tile running up the wall, and the calculator on this page starts with the floor, because that is the measurement the room hands it. If you are tiling a wall, type the wall.
A single eight foot wall taken to the ceiling at eight feet is 64 square feet, which is more tile than the entire floor of this bathroom. A wet wall around a tub, say five feet wide by six feet high on three sides, is a different sum again. Switch to Tile on the strip, put the run in the length field and the height in the width field, and read the box count for that surface on its own. Then add the surfaces up yourself. Doing it surface by surface is slower and it is the only way it comes out right.
The trowel changes the bag count more than the room does
This is the number nobody thinks to ask about. The published coverage for a 50 pound bag is 85 to 95 square feet with a quarter by quarter by quarter inch square notch trowel, and 60 to 67 square feet with a quarter by three eighths by quarter inch square notch. That is roughly a third less coverage from the same bag, decided entirely by which trowel the tile calls for. Larger format tile generally wants the bigger notch.
So if somebody tells you a bathroom takes two bags where this page says one, the disagreement is probably about the trowel, not about the room, and that is a question with an answer rather than an argument. The trowel size is a field on the tile calculator. Change it and watch the bag count move.
What this page refuses to guess about a bathroom
More than in any other room. It does not know what is behind your tile, whether the substrate is suitable, or whether the last person waterproofed anything. Mortar data sheets carry an explicit list of surfaces they will not bond to, and reading that list for the product you are actually buying matters more than any count on this page. It does not know about the plumbing, the fall to the drain, or the ventilation, and those are the three things that decide whether a beautiful bathroom stays beautiful.
What it does is tell you, before you have spoken to anybody, that this room is three boxes and a bag and a gallon rather than an unknown. That is a small thing and it is the difference between starting and not starting.
What people ask about a bathroom
How many boxes of tile for a small bathroom floor?
For an eight by five floor, three boxes at 15 square feet each, which is 40 square feet of floor covered by 45 square feet bought. Box coverage is not standardised and changes line to line inside the same manufacturer, so read the carton in front of you and type that number in.
How many bags of thin-set does a bathroom take?
One 50 pound bag covers 85 to 95 square feet with a quarter inch square notch trowel and 60 to 67 with a quarter by three eighths, both published by the manufacturer. A 40 square foot floor is one bag either way. A floor plus a tiled wet wall may not be.
How much paint does a bathroom need?
One gallon covers two coats on this eight by five room at both ends of the published 350 to 400 square feet per gallon. If you tile part of the wall, subtract that area by typing a lower ceiling height or a larger openings figure, because painted square footage is what the calculation wants.
Why does such a small room still need a whole gallon and a whole bag?
Because nothing here is sold by the square foot. The smallest unit you are allowed to buy is a box, a bag or a gallon, and a small room hits that floor immediately. It is the single biggest reason bathrooms feel disproportionately expensive per square foot, and it is arithmetic rather than anybody overcharging you.
Can I tile straight onto the old floor?
That depends on what the old floor is, and the mortar data sheet for the product you buy names the surfaces it will not go over. This site counts material and knows nothing about your substrate, so treat that list as the document that decides, not this page.
The calculators this room opens
Another room
An estimate, not a quote. Everything above is arithmetic on the measurements you typed and on figures printed in the documents cited on this page. Site conditions, layout, substrate and local code all move the real number, and the label on the box in your hand outranks all of it. Measure twice.