How this tile calculator works
Tile is bought three ways at once — by the piece, by the box, and with the setting materials — and all three hang off the same waste-inclusive area:
tiles = buy area ÷ tile ft² · boxes = buy area ÷ box ft² · thinset = buy area ÷ 80/bag
At the defaults — a 10 × 12 ft floor in 12 × 12 tile — that’s 132 tiles, 9 boxes and 2 bags of thinset, about $405; the full chain is in the layout math section below.
Tile, thinset and the rest of the setting kit
A tile job is the tile plus a stack of setting materials, and skipping any one of them stalls the install:
The tile
Ceramic for walls and light-traffic floors, porcelain for durability and wet areas, natural stone for looks and a sealing routine. Format drives the count and the waste — big-format and plank tile cut more, mosaics on sheets install by the square foot.
Substrate and membrane
Tile needs a stable base: cement backer board or an uncoupling membrane over subfloor, waterproofing in showers. It’s the layer that decides whether the floor cracks, and it’s a separate order from the tile.
Thinset mortar
The bonding layer, troweled to a notch matched to the tile size — about 80 ft² per 50 lb bag at a ¼ in notch, less as the notch grows. Modified or unmodified depends on the tile and membrane; the bag says.
Grout
Cementitious or epoxy, sanded for wider joints, filling the gaps the spacers held. Coverage depends on tile size and joint width, not just floor area — the bag chart is the guide.
Spacers, trim and sealer
Spacers or a leveling system set the joints; bullnose or metal edge trim finishes the edges; penetrating sealer protects stone and grout. The small lines that make the job look finished.
How many tiles per square foot?
Table 1 gives the piece count per 100 ft² by tile size, before waste — the number the engine scales to your room and adds the waste on top of.
| Tile size | Per 100 ft² |
|---|---|
| 3 × 6 subway | 800 |
| 12 × 12 | 100 |
| 12 × 24 | 50 |
| 18 × 18 | 45 |
| 24 × 24 | 25 |
How to measure for tile
Measure the area, pick the tile, set the waste to the pattern — the calculator does the piece, box and bag counts.
- Measure length and width of the floor (or length × height of a wall or backsplash). Odd rooms break into rectangles — total them with the square footage calculator.
- Pick the tile size — the chips set the face area, and the piece count re-runs.
- Set the waste: 10% for a straight lay in a simple room, 15% for diagonal, herringbone, or lots of cuts and niches.
- Enter your box coverage from the carton — it varies by tile, and it’s what the box count divides by.
- Buy the whole job from one dye lot up front; the waste allowance is also your repair stash for the life of the floor.
- Match the thinset notch to the tile — the 80 ft²/bag figure is a ¼ in notch; big tile and bigger notches use more.
Worked example: tile for a 10 × 12 floor
The default floor, worked line by line — 10 × 12 ft in 12 × 12 tile, 10% waste, 15 ft² a box:
buy = 120 × 1.10 = 132 ft²
tiles = 132 ÷ 1 = 132 tiles
boxes = 132 ÷ 15 = 8.8 → 9 boxes ≈ $405
thinset = 132 ÷ 80 = 1.65 → 2 bags
The 10% waste — 12 extra square feet here — is doing two jobs: it covers the perimeter cuts that don’t yield a usable offcut, and it leaves you a handful of spare tiles from the right dye lot for the cracked-tile repair years from now. Skip it and a single miscut on the last row means a second trip and a color that no longer matches.
What this tile estimate doesn’t include
- Backer board or membrane. Cement board or uncoupling mat over the subfloor — a separate order.
- Grout. Figured by tile size and joint width off the maker’s chart, not floor area.
- Waterproofing. Shower pans, membranes and corners in wet installs.
- Trim tile. Bullnose, edge and transition pieces beyond the field count.
- Spacers, sealer and tools. Leveling systems, penetrating sealer, a wet saw rental.
- Demo and prep. Tearing out the old floor and flattening the substrate.
- Labor. Setting is skilled work — installed tile commonly runs $10–20 per ft².
Tile FAQ
How many tiles do I need for a 120 square foot floor?
In 12 × 12 in tile: 132 with 10% waste (120 exact). The same floor takes 66 pieces of 12 × 24, 33 of 24 × 24, or about 1,056 subway tiles — the calculator recomputes for any size and shows boxes by your box coverage.
How much extra tile should I buy for waste?
10% for a straight lay in a simple room; 15% for diagonal, herringbone and rooms with many cuts or niches. Buy it all up front from one dye lot — matching a lot later is the classic tile disaster.
How do I calculate tile for a backsplash or wall?
Same area math, turned vertical: length × height of the tiled area, minus the window and outlet cutouts, times your waste. Backsplashes and mosaic sheets run more waste (15%) because of all the edge cuts around cabinets and outlets. Enter the wall area as the floor size and read tiles and thinset the same way.
How much thinset per square foot?
Plan on a 50 lb bag per ~80 ft² with a ¼ in square-notch trowel — two bags for the default floor. Larger tile wants larger notches (and more thinset): check the trowel size your tile and substrate call for.
How much grout do I need for tile?
Grout depends on tile size and joint width, not floor area alone — big tiles with thin joints use little, small mosaics with wide joints use a lot. As a rough guide, a 50 lb bag grouts 100–200 ft² of 12 in tile at a 1/8–3/16 in joint. The bag maker’s coverage chart, keyed to tile size and joint, is the number to trust.
How many square feet are in a box of tile?
Commonly 12–20 ft² depending on tile size — it is printed on the box. Type your box coverage in and the calculator orders whole boxes over the waste-inclusive area.
What size trowel for which tile?
Notch size tracks tile size: a ¼ in square-notch for tile up to about 12 in, a ½ in for 12–16 in, and a larger or slotted trowel plus back-buttering for big-format tile to hit the coverage the standards want (80% dry areas, 95% wet). Bigger notches spread more thinset — which is why the per-bag coverage drops as the tile grows.
Sources and standards
- TCNA Handbook: the Tile Council of North America methods behind substrate, thinset coverage and waterproofing practice.
- ANSI A108 / A118: the installation and mortar standards, including the 80% (dry) / 95% (wet) coverage requirements.
- Manufacturer trowel and coverage charts: notch size by tile, and the ~80 ft² per bag figure this calculator uses.
- Dye-lot practice: why the waste allowance doubles as a from-the-same-lot repair stash.
Embed this tile calculator on your site
Run the tile calculator on your own site, free. Paste the snippet where you want it; the visible credit link is the only condition.