How to use the tile calculator
- Enter the room length and width (for walls, the wall length and height), or enter the total area if you already know it.
- Enter the tile size and your grout joint width. Typical joints: 1/16–1/8 in (1.5–3 mm) for rectified porcelain, 3/16–1/4 in (5–6 mm) for rustic tiles.
- Choose the layout. Diagonal and herringbone patterns need more cuts, so the calculator adds more extra.
- Enter tiles per box and the price to see boxes and cost.
Tile formula
Tile coverage = (Tile length + grout) × (Tile width + grout) Tiles = Area ÷ Tile coverage Tiles to buy = Tiles × (1 + extra %) → round up Boxes = Tiles to buy ÷ tiles per box → round up
Worked example
A 12 × 10 ft kitchen floor with 12 × 12 in tiles, 1/8 in grout, straight layout, 10 tiles per box:
- Area = 120 ft² = 17,280 in²
- Each tile with grout = 12.125 × 12.125 = 147.0 in²
- Tiles = 17,280 ÷ 147.0 = 117.5
- +10% = 129.3 → 130 tiles = 13 boxes
How much extra tile for each layout
| Layout | Typical extra | Why |
|---|---|---|
| Straight / grid | 10% | Cuts only at the edges |
| Brick / offset (⅓ or ½) | 10% | Edge cuts plus offset ends |
| Diagonal (45°) | 15% | Triangular cuts along every wall |
| Herringbone / chevron | 20%+ | Angled cuts at all edges, more breakage |
| Large-format (over 24 in / 600 mm) | +5% more | Each broken tile is a big loss |
Tips for buying tiles
- Check the batch (shade/lot) number on every box. Different batches can vary noticeably in colour.
- Keep spare tiles after the job — exact matches are often impossible to find a few years later.
- Plan the layout from the centre so you don't end up with thin slivers along a visible wall.
- Also buy adhesive (thinset) and grout. As a rough guide, one 50 lb (20–25 kg) bag of thinset covers about 50–90 ft² (5–8 m²) depending on the trowel size — check the bag.
Tiling walls, splashbacks and showers
For walls, enter the wall length and the height you want to tile. Measure each wall separately and add them together with “I know the area”. Subtract windows and doors, but do not subtract areas hidden behind kitchen units unless you are sure you will never need tile there. Shower walls usually run from the floor to at least 6–7 ft (1.8–2.1 m). Remember trim and edge pieces (bullnose, metal profiles) are bought by length, not area, so measure all exposed edges separately. If you are tiling the floor and walls of a bathroom, calculate them separately — wall and floor tiles are rarely the same product, and floor tiles need a higher slip rating.