Short answer
A standard 5×8 bathroom floor is 40 sq ft. Add the standard 10% waste and you need 44 sq ft of tile — 44 tiles at 12×12 (5 boxes of 10), or 22 tiles at 12×24. Measure wall to wall, add 10%, and always round up to whole boxes.
Tiles by bathroom floor size
| Bathroom floor | Floor area | With 10% waste | 12×12 tiles | Boxes (assuming 10 per box) |
|---|---|---|---|---|
| 5×5 ft | 25 sq ft | 27.5 sq ft | 28 | 3 |
| 5×7 ft | 35 sq ft | 38.5 sq ft | 39 | 4 |
| 5×8 ft | 40 sq ft | 44 sq ft | 44 | 5 |
| 6×8 ft | 48 sq ft | 52.8 sq ft | 53 | 6 |
| 8×10 ft | 80 sq ft | 88 sq ft | 88 | 9 |
Tile counts are rounded up — you cannot buy part of a tile, and the extra covers cuts and breakage.
How to measure your bathroom
Measure the length and width of the floor, wall to wall, and multiply. For an L-shaped bathroom, split the floor into rectangles, work out each one, and add the areas together.
Do not subtract the toilet or vanity footprint. Those areas are small, the tile under them is usually laid anyway, and the extra covers the cuts around them. Running short mid-project is far more expensive than a few spare tiles.
What about wall tiles?
Wall tile uses the same math, just measured per wall. One shower wall 5 ft wide and 7 ft high is 35 sq ft — with 10% waste that is 38.5 sq ft, so 39 tiles at 12×12 (4 boxes). Measure each wall separately and add them up; shower walls are often tiled to about 7 ft, or to the ceiling for a full-height look.
How much extra tile should you buy?
The standard waste allowance is 10%. Go to 15% if the tiles are laid diagonally, the room has lots of corners and cuts, or you are using a pattern like herringbone. Always buy whole boxes, and keep a few spare tiles after the job — finding an exact match months later for a cracked tile is often impossible.
What does it cost?
Installed tile flooring typically costs $10–$30 per sq ft, depending on the tile type, layout, and labor. For a 5×8 bathroom floor (40 sq ft), that works out to roughly $400–$1,200 installed. See the full breakdown in our tile installation cost guide.
Frequently asked questions
How much extra tile should I buy for a bathroom?
10% over the measured area is the standard rule. Use 15% for diagonal layouts, heavy patterns, or rooms with many corners.
Should I subtract the toilet and vanity area?
No. Measure wall to wall. The small saving is not worth the risk of running short, and the tile under fixtures is usually laid anyway.
How many 12×24 tiles do I need for a 5×8 bathroom?
22 tiles (44 sq ft ÷ 2 sq ft per tile), so about 3 boxes — check the number of tiles per box on the product you buy. Larger tiles mean fewer tiles to lay, but also fewer chances to hide uneven floors.
What about mosaic sheets?
The same square-foot math applies. Most mosaic sheets cover 1 sq ft each, so a 5×8 floor needs about 44 sheets — but always check the coverage stated on the sheet you are buying, since it varies.
Run your exact numbers
Every bathroom is a different size, so run your own measurements through the free tile calculator — it works out the tiles, boxes, and cost for your exact room.