Calculate how many tiles to order for any project from the room dimensions, tile size, and a waste allowance.
Usage Tip
Buy from one production lot so shade and size match, and keep a few spare tiles for future repairs.
tile area = (tile L ÷ 12) × (tile W ÷ 12)
tiles = round up( room area ÷ tile area × (1 + waste ÷ 100) )
The result rounds up to whole tiles.
How Much Tile Do I Need?
Find the area, add a waste factor for cuts and breakage, then divide by the coverage per tile (for a tile count) and per box (for boxes). Tile is sold by the box, so you round up to whole boxes – and buy a little extra from the same lot, because dye lots vary.
Tile Size Coverage
Smaller tiles mean far more pieces (and more grout). Approximate tile count per 100 sq ft, before waste:
| Tile size | Each covers | Per 100 sq ft |
|---|---|---|
| 3×6 subway | 0.125 sq ft | about 800 |
| 4×4 | 0.11 sq ft | about 900 |
| 6×6 | 0.25 sq ft | about 400 |
| 12×12 | 1 sq ft | about 100 |
| 12×24 | 2 sq ft | about 50 |
| 24×24 | 4 sq ft | about 25 |
Tile Waste Factor Guide
| Layout | Waste |
|---|---|
| Straight lay | 10% |
| Diagonal | 15% |
| Herringbone | 15-20% |
| Complex cuts / many obstacles | 20%+ |
Large-format and diagonal layouts waste more because the offcuts are bigger and harder to reuse. Always keep a spare box of each tile from the same lot for future repairs.
Grout Coverage Guide
Grout fills the joints, so it depends on tile size, joint width, and depth – not just area. Small tiles and wide joints use much more. As a rough guide a 25 lb bag of sanded grout covers about 200 sq ft of 12×12 tile at a 1/8 in joint, but only about 50 sq ft of mosaic. Typical joints: 1/16 in mosaic/glass, 1/16-1/8 in subway/wall, 1/8-1/4 in floor tile.
Thinset / Mortar Coverage
Thinset coverage depends on the trowel notch, which scales with tile size. As a guide per 50 lb bag:
| Tile size | Trowel | Coverage per 50 lb bag |
|---|---|---|
| Mosaic – 6 in | 1/4 in | about 45-50 sq ft |
| 8 – 12 in | 1/4 x 3/8 in | about 40 sq ft |
| 12 – 16 in | 1/2 in | about 35 sq ft |
| Large-format (18 in+) | 1/2 in+ / LFT | about 30 sq ft |
Large-format tiles need a bigger notch and often a medium-bed mortar, so coverage drops. Back-butter big tiles for full support.
Tile Layout Pattern Guide
Straight (grid): simplest, least waste. Diagonal (45 degrees): hides out-of-square rooms but cuts every edge tile. Herringbone: striking with rectangular tile, highest waste and labor. Running bond (offset/brick): classic for subway and plank tile; keep the offset to about a third for long tiles to avoid lippage. Pick the pattern before buying – it changes the waste factor.
Wall Tile vs Floor Tile
Floor tile is rated for foot traffic (check the PEI rating) and slip resistance; wall tile is lighter and can be more delicate. Floor tile can usually go on walls, but wall tile is generally not strong enough for floors. Walls also use narrower joints and unsanded grout, while floors take wider joints and sanded grout.
Shower & Backsplash Estimating
For a shower, measure each wall and the floor separately and add them up, then add 15% waste for the cuts around niches, benches, and the curb – and use a waterproof setup with epoxy or well-sealed grout. A kitchen backsplash is small but cut-heavy (outlets, window, range), so keep the waste factor at about 15% even though the area is tiny. Examples: a 30 sq ft backsplash of subway tile is roughly 250 tiles plus a 1-2 boxes; a three-wall shower surround is often 80-110 sq ft of wall tile.
Common Tile Measuring Mistakes
- Too little waste – cuts and breakage are guaranteed; 10% minimum, more for patterns.
- Forgetting grout and thinset – the tile is only part of the order.
- Mixing dye lots – buy all the tile (plus spare) from one lot.
- Ignoring pattern – diagonal and herringbone need noticeably more tile.
- Not measuring surfaces separately – add up shower walls and floor individually.
Frequently Asked Questions
How many tiles do I need?
Area times your waste factor, divided by the area of one tile. Enter your surface, tile size, and pattern above for the count and boxes.
How much waste should I add for tile?
About 10% for a straight lay, 15% for diagonal, and 15-20%+ for herringbone or complex cuts.
How much grout and thinset do I need?
Grout depends on tile size, joint, and depth; thinset on tile size and trowel. The calculator estimates both from your inputs.
How many tiles are in a box?
It varies by tile – check the box coverage in square feet. A box of 12×12 often covers about 15 sq ft; subway boxes about 10-12.
Can I use wall tile on the floor?
Usually not – wall tile is often too soft. Floor tile can typically be used on walls, though.
How much extra tile should I buy?
Your waste factor plus at least one spare box from the same lot for repairs.
Related Flooring & Tile Calculators
Note: tile, box, grout, and thinset figures are planning estimates and vary by product, box coverage, tile size, joint, pattern, trowel, and cutting. Confirm coverage on the box, buy all tile from one dye lot with a spare box, and follow the manufacturer and setting-material instructions. General DIY guidance, not a professional measure.