A 10 × 12 ft floor in 12 × 24 in porcelain with ⅛ in joints, laid offset, takes 69 tiles: 59 to cover the 120 square feet, 65 once the cuts at the walls are counted, and 69 with 5 % for breakage. That is 9 boxes of 8, three 50 lb bags of thinset with a ½ in trowel and about 7 lb of grout. The calculator above does the same for floors, walls or any area, in four patterns, and draws the layout.
How the calculator works
Choose the surface — a floor by its length and width, walls by the room and the tile height, or any area — and deduct doors and windows on walls. Enter the tile size, joint and thickness, pick the pattern, the breakage reserve and the box coverage, then the trowel and the grout. The result counts tiles, boxes, thinset bags and grout, and the drawing shows the pattern on the surface.
Tiles
Each tile with its joint takes (length + joint) × (width + joint) of surface: a 12 × 24 in tile with ⅛ in joints takes 2.03 ft². Dividing the area by that gives the tiles on the area. The pattern adds the cuts at the edges:
| Pattern | Cuts | Notes |
|---|---|---|
| Straight | 5 % | Joints in line; fewest cuts |
| Offset | 10 % | Brick-style; keep the offset to a third on long tiles to avoid lippage |
| Diagonal | 15 % | At 45°; triangles along every wall |
| Herringbone | 15 % | Rectangular tiles in a zigzag |
The breakage reserve comes on top: tiles that crack while cutting, rejects, and a few spares to keep for repairs.
Thinset and trowel
The bigger the tile, the deeper the notch: ¼ × ¼ in up to about 8 in, ¼ × ⅜ in up to about 16 in, ½ × ½ in above — and back-buttered so the mortar covers the whole tile. A 50 lb bag covers roughly 90, 65 and 45 ft² with those notches; the bag label has the exact figure.
Grout
The grout fills joints as deep as the tile is thick. Per area it is (L + W) ÷ (L × W) × joint × depth × density — small tiles mean more joints and more grout. Use sanded grout for joints over ⅛ in and unsanded up to ⅛ in (ANSI A108.10).
Common mistakes
- Counting tiles without the joint. It overstates the tiles slightly; forgetting the cuts understates them a lot.
- Mixing lots. Buy all boxes from one production lot — shade varies between lots.
- Too small a trowel for large tile. Hollow spots crack under load.
For grout alone, use the Grout Calculator.