How to use this tile calculator
- Enter the area to tile. For an L-shaped room or several walls, click Add another area for each part. If you only know the total, see our square footage calculator.
- Enter the tile size and the grout joint width (the size of your tile spacers).
- Choose your layout. It sets a typical waste allowance, which you can change.
- Add tiles per box from the box label to see how many whole boxes to buy.
- Optionally add a price and the tile thickness to estimate cost and grout.
Tile calculation formula
Each tile covers its own face plus half the joint on every side, so the joint is added to the tile’s length and width.
Tiles = Area ÷ Tile coverage
Tiles to buy = Tiles × (1 + Waste % ÷ 100), rounded up
Boxes = Tiles to buy ÷ Tiles per box, rounded up
Worked example: a 10 × 12 ft bathroom floor
- Floor area: 10 × 12 = 120 sq ft
- Tile: 12 × 12 in with a 1/8 in joint, so each tile covers 12.125 × 12.125 = 147.02 sq in (1.02 sq ft)
- Tiles before waste: 120 ÷ 1.02 = 117.5
- With 10% extra: 117.5 × 1.10 = 129.3, so buy 130 tiles
- At 10 tiles per box: 13 boxes
- Grout, with 3/8 in thick tiles: about 4.1 kg (9.1 lb)
Tiles per 100 sq ft and per 10 m²
Before waste, with a typical grout joint. Add 10–20% depending on your layout.
| Tile size | Joint | Tiles per 100 sq ft |
|---|---|---|
| 3 × 6 in (subway) | 1/16 in | 776 |
| 4 × 4 in | 1/16 in | 873 |
| 6 × 6 in | 1/8 in | 384 |
| 6 × 24 in (plank) | 1/8 in | 98 |
| 12 × 12 in | 1/8 in | 98 |
| 12 × 24 in | 1/8 in | 50 |
| 18 × 18 in | 3/16 in | 44 |
| 24 × 24 in | 1/8 in | 25 |
| Tile size | Joint | Tiles per 10 m² |
|---|---|---|
| 10 × 10 cm | 2 mm | 962 |
| 20 × 20 cm | 3 mm | 243 |
| 30 × 30 cm | 3 mm | 109 |
| 30 × 60 cm | 3 mm | 55 |
| 60 × 60 cm | 3 mm | 28 |
| 60 × 120 cm | 2 mm | 14 |
Waste allowance by layout
| Layout | Typical extra | Why |
|---|---|---|
| Straight / grid | 10% | Cuts only at the edges |
| Brick / offset | 10% | Offcuts can often start the next row |
| Diagonal | 15% | Every edge tile is cut at an angle |
| Herringbone / chevron | 15–20% | Many angled cuts and more breakage |
These are common starting points. Small rooms, lots of obstacles and fragile or large-format tiles may need more.
Estimating grout
Grout fills the joints between tiles, so the amount depends on how much joint there is per square metre and how deep it is. A widely used formula, with all sizes in millimetres, is:
The 1.7 is an approximate density for cement-based grout. Typical results:
| Tile (mm) | Thickness | Joint | Grout per m² |
|---|---|---|---|
| 100 × 100 | 6 mm | 2 mm | ≈ 0.41 kg |
| 150 × 150 | 7 mm | 5 mm | ≈ 0.79 kg |
| 300 × 300 | 8 mm | 3 mm | ≈ 0.27 kg |
| 300 × 600 | 9 mm | 3 mm | ≈ 0.23 kg |
| 600 × 600 | 10 mm | 3 mm | ≈ 0.17 kg |
Grout products differ, so treat this as a guide and check the coverage chart on the bag. Epoxy and lightweight grouts have different densities.
Tips before you buy tile
- Buy from one batch. Check the shade or lot number on every box. Colour can vary between production runs.
- Lay tiles out dry first. A dry layout shows where cuts will fall so you can avoid thin slivers at doorways.
- Keep spares. Store a few leftover tiles for future repairs. Discontinued tiles are very hard to match.
- Check returns. Many stores take back unopened boxes, so rounding up is usually low-risk.
- Prepare the surface. A flat, solid, clean substrate matters more than the tile itself for a long-lasting job.
Laying planks or laminate instead? Use our flooring calculator.
Frequently asked questions
How many 12x12 tiles do I need for 100 square feet?
With no grout joint, exactly 100 tiles, because each 12 × 12 in tile covers 1 sq ft. With a 1/8 in joint each tile effectively covers a little more, so you need about 98 tiles, then add 10% for cuts and breakage: about 108 tiles in total.
How much extra tile should I buy?
Around 10% for a straight or brick layout and 15–20% for diagonal or herringbone patterns, small rooms with lots of cuts, or large-format tiles that break easily. Keeping a few spare tiles from the same batch also makes future repairs much easier.
Does grout joint width change how many tiles I need?
Yes, slightly. Each tile plus its joint covers more area than the tile alone, so wider joints mean fewer tiles. The effect is biggest with small tiles: 4 × 4 in tiles with a 1/8 in joint need about 6% fewer tiles than the raw area suggests, while 24 × 24 in tiles change by only about 1%.
How much grout do I need?
It depends on tile size, tile thickness and joint width. A common estimate is kg per m² = (L + W) ÷ (L × W) × joint width × tile thickness × 1.7, with all sizes in millimetres. Small tiles and wide joints use far more grout than large tiles with narrow joints. Always check the coverage chart on your grout bag.
How do I calculate tiles for a wall?
Measure the height and width of each wall section and enter each as a rectangle. Add triangles or extra areas for odd shapes. The calculator adds areas together, so for large windows or doors you won’t tile, measure the tiled sections around them separately instead. The calculation is the same as for a floor.
Should I buy tiles by the box or individually?
Most tile is sold by the box, and the price is often quoted per square foot or square metre. Enter the number of tiles per box to see how many whole boxes to buy. Buy every box from the same batch (shade/lot number) so the colour matches.
Last reviewed November 5, 2026.