How Much Tile for a Bathroom Floor?
The short answer: 5 boxes of 12x12 tile for a typical bathroom, plus adhesive and grout.
A 40 square foot bathroom floor needs 5 boxes of 12x12 tile, 1 bag of thinset and 1 bag of grout. That assumes 10 tiles per box and a 10 % waste allowance. The grout is the only figure that moves much with your tile choice — small tiles need several times as much.
Estimates only. Textured walls, high ceilings, sprayers and major colour changes can all increase the amount you need. Always buy slightly more than the calculation suggests.
Tile needed by bathroom floor size
| Area | Surface | Tile size | Tiles | Boxes | Tile cost |
|---|---|---|---|---|---|
| Small bathroom, 25 sq ft, 12x12 | 25 sq ft | 12" × 12" | 28 | 3 boxes | $105 |
| Standard bathroom, 40 sq ft, 12x12 | 40 sq ft | 12" × 12" | 44 | 5 boxes | $175 |
| Large bathroom, 80 sq ft, 12x12 | 80 sq ft | 12" × 12" | 88 | 9 boxes | $315 |
| Standard bathroom, 40 sq ft, 12x24 | 40 sq ft | 12" × 24" | 22 | 3 boxes | $105 |
| Standard bathroom, 40 sq ft, 6x6 | 40 sq ft | 6" × 6" | 176 | 9 boxes | $315 |
| Large bathroom, 80 sq ft, diagonal 12x12 | 80 sq ft | 12" × 12" | 92 | 10 boxes | $350 |
Straight lay at 10 % waste, 10 tiles per box. The last row shows how a larger tile changes the box count.
Measure the floor, not the room
Bathroom floors are rarely a clean rectangle. Measure the actual tiled area, and break it into rectangles if the room is L-shaped.
Two things to subtract or add depending on your plan:
- The vanity. If it sits on legs or you are tiling underneath it, include its footprint. If it is a fitted unit going back on top, you can skip it — but tiling under it anyway is cheap insurance for future changes.
- The toilet and bath. Tile right up to them, and include the area under them in your measurement. Tiling around a toilet and hoping to cut in later never looks right.
Add the door threshold: a strip of tile under the door is normal, and it is easy to forget when measuring.
The right adhesive for a bathroom floor
Bathroom floors are wet areas, and the adhesive has to match.
- Modified thinset is the standard choice for a bathroom floor over a cement backer board or a concrete slab.
- Over a wooden subfloor, you need a modified thinset rated for plywood, and the subfloor must be stiff enough that it does not flex. Deflection is the number one cause of cracked tile floors.
- Do not use premixed "mastic" on a floor. It is for walls only. On a floor it never fully hardens and tiles come loose.
The calculator asks for coverage per bag. On a bathroom floor with a flat substrate a 1/4" trowel is normal, which is about 80 to 95 square feet per 50 lb bag.
Frequently asked questions
How much tile do I need for a bathroom floor?
A 40 sq ft bathroom needs 44 tiles of 12x12 with a 10 % waste allowance, which is 5 boxes at 10 per box, plus 1 bag of adhesive and 1 bag of grout.
How many boxes of tile for a small bathroom?
A 25 sq ft bathroom floor in 12x12 tile needs 28 tiles, which is 3 boxes at 10 per box.
Should I tile under the toilet and vanity?
Tile up to and around them, and include their footprint in your measurement. Tiling around a toilet and cutting in later never lines up properly.
What adhesive should I use on a bathroom floor?
Modified thinset, and a version rated for plywood if your subfloor is timber. Never use premixed mastic on a floor — it stays soft and tiles lift.