Tile Calculator
Estimates only. Confirm the box coverage and piece count on your product label before ordering.
For a straight-set floor, buy about 10% more tile than your bare square footage; for diagonal or herringbone layouts, plan on 15–20% to cover the extra angled cuts. A 100 sq ft floor in 12 × 12 tile needs 100 tiles plus waste — about 110 tiles, or roughly 8 boxes at 15 sq ft per box. Enter your area, tile size, grout joint, and layout below for exact tiles, boxes, and cost.
Tile coverage by size
| Tile size | Area per tile | Tiles per sq ft | Tiles per 100 sq ft | Common use |
|---|---|---|---|---|
| 4" × 4" | 0.11 sq ft | 9.0 | 900 | Wall and accent tile |
| 3" × 6" (subway) | 0.125 sq ft | 8.0 | 800 | Backsplashes, wall tile |
| 6" × 6" | 0.25 sq ft | 4.0 | 400 | Floor and wall tile |
| 6" × 24" (plank) | 1.0 sq ft | 1.0 | 100 | Wood-look plank floors |
| 12" × 12" | 1.0 sq ft | 1.0 | 100 | Standard floor tile |
| 12" × 24" | 2.0 sq ft | 0.5 | 50 | Large-format floors |
| 18" × 18" | 2.25 sq ft | 0.44 | 45 | Large open-room floors |
| 24" × 24" | 4.0 sq ft | 0.25 | 25 | Extra-large-format floors |
How to estimate tile
Tile is estimated by area, not volume. Divide the surface area in square feet by the area one tile covers to get the raw tile count: a tile's coverage is width × length ÷ 144 square feet, so a 12 × 12 tile covers exactly 1 sq ft and a 3 × 6 subway tile covers 0.125 sq ft. Then round up and add a waste allowance. Suppliers sell tile by the box, so divide your total area (including waste) by the coverage printed on the box and round up to whole boxes.
Grout joints change the count
The grout joint adds to each tile's footprint on the floor. A 12 × 12 tile set with a 1/4-inch joint actually occupies about 12.25 × 12.25 inches, or roughly 1.04 sq ft — so a wider joint means slightly fewer tiles cover the same room. This calculator adds your joint width to the tile dimensions before counting. Ignoring grout entirely is a safe over-estimate (you buy a hair more), but modelling it is more precise on large jobs. Your tile spacer size is the joint width, so enter the spacer you plan to use — 1/16 and 1/8 inch for walls and rectified tile, 3/16 and 1/4 inch for floors and rustic tile. Use unsanded grout for joints 1/8 inch or narrower and sanded grout for wider joints. To size the grout itself, run your tile size and joint width through the grout calculator for the bags you need.
Waste by layout pattern
The layout drives how much extra you buy. A straight, grid-set floor wastes about 10% to edge cuts and the occasional cracked tile. A diagonal (45°) layout pushes that to 15–20% because the perimeter cuts leave larger unusable offcuts, and interlocking patterns like herringbone and chevron sit at the top of that band — budget up to 20%. Pick your pattern above and the overage prefills to match. For a natural flagstone patio instead of manufactured tile, run the stone calculator to get tonnage by stone type.
Estimating by application
The math is the same for every job — area ÷ tile coverage, plus waste — but what you measure and how much you over-order shifts with the surface.
- Floor tile. Measure the room's length × width for your area. This is the baseline case above: 10% waste for a straight set, more for diagonal and patterned layouts. Large-format floor tile (12 × 24 and up) is less forgiving of subfloor dips, but the count is the standard area ÷ coverage.
- Wall and backsplash tile. Measure each wall as height × width instead of a floor footprint, then subtract windows, outlets, and the run behind cabinets or a range hood. A kitchen backsplash is usually a narrow band — countertop to upper cabinets, often about 18 inches tall — so multiply that height by the counter run. Subway (3 × 6) is the classic wall and backsplash tile at 8 tiles per square foot; a brick-offset set wastes about 10%, herringbone more.
- Shower tile. Add every surface: each wall as height × width up to the tiled height, plus the pan or floor, plus any curb and bench. Don't subtract the niche — you tile its inside faces too, so leave it in as a small over-estimate. Showers lean on smaller tile and mosaics on the floor for slope and grip, so budget 15% waste, and up to 20–25% for mosaic sheets or a busy pattern.
- Drop-ceiling tile. Suspended-ceiling tiles come in a 2 × 2 ft grid tile (4 sq ft each, so room area ÷ 4) and a 2 × 4 ft tile (8 sq ft each, area ÷ 8). Enter those as your tile size in inches (24 × 24 or 24 × 48). Edge tiles get field-cut to the border, so keep a 10% allowance even though the grid itself is regular. Solid glue-up ceiling tiles use the same area math.
- Deck and carpet tile. Interlocking deck tiles and carpet squares are sold by the piece, not by the box, and each covers its own face size — a 12 × 12 in carpet tile is 1 sq ft, a 20 × 20 cm deck tile about 0.43 sq ft. Divide your area by one tile's coverage, round up, and add roughly 5–10%; there's no grout joint, but perimeter pieces still need cutting.
Common mistakes
- Buying by bare square footage. Skipping the waste allowance leaves you short mid-job. A second trip risks a different dye lot with a visible color shift, so always order the overage in one go.
- Not keeping attic stock. Whole boxes round up, so you'll have leftover tiles — keep them. A cracked tile years later is impossible to match once the line is discontinued.
- Ignoring the pattern. Ordering a herringbone floor at the straight-set 10% is the most common way to run out. Angled cuts waste far more material.
- Irregular rooms. For an L-shape, split it into rectangles, run each, and add the tile counts. Subtract large fixed features like a kitchen island footprint from the area.
Frequently asked questions
How do I calculate how many tiles I need?
Divide the total area you're covering (in square feet) by the area of one tile in square feet, then round up and add a waste allowance. One tile's area in square feet is its width times its length in inches, divided by 144. For example, a 12 × 12 in tile is exactly 1 sq ft, so a 120 sq ft floor needs 120 tiles before waste. Add 10% for a straight layout, or 15–20% for diagonal and patterned installs, and round up to whole boxes.
How much extra tile should I buy for waste?
Buy 10% extra for a standard straight-set layout, and 15–20% extra for diagonal or patterned layouts like herringbone and chevron. The waste covers perimeter cuts, the occasional broken tile, and attic stock for future repairs. Angled patterns waste more because 45-degree cuts at the walls leave larger unusable offcuts, so plan toward the top of that range. It's cheaper to keep a few spare tiles than to reorder a partial box in a dye lot that may no longer match.
How many 12x12 tiles do I need for 100 square feet?
You need 100 of the 12 × 12 in tiles for 100 square feet before waste, because each 12 × 12 tile covers exactly one square foot. Add your waste allowance on top: 110 tiles at 10% for a straight layout, or about 115–120 at 15–20% for a diagonal or patterned layout. Then round up to whole boxes based on the coverage printed on the box.
How many subway (3x6) tiles are in a square foot?
There are 8 subway tiles per square foot, since a 3 × 6 in tile covers 0.125 sq ft (3 × 6 ÷ 144). That works out to 800 tiles per 100 square feet before waste. Subway tile is usually run in a brick-offset or herringbone pattern, so budget 10–15% waste depending on the layout.
Do I need to account for grout lines when calculating tile?
Grout joints make each tile cover slightly more floor than its face size, so accounting for them slightly reduces the tile count. A 12 × 12 in tile with a 1/8 in grout joint effectively covers about 1.02 sq ft instead of 1.0. Ignoring grout is a safe over-estimate — you'll simply buy a little extra — but modeling the joint is more precise. Use unsanded grout for joints 1/8 in or narrower and sanded grout for wider joints.
How much more tile do I need for a diagonal or herringbone pattern?
Plan on up to 20% extra tile for diagonal and herringbone or chevron patterns, versus 10% for a straight layout. Angled installs require cutting tiles at 45 degrees around the entire perimeter, and those triangular offcuts usually can't be reused elsewhere. Herringbone and chevron also generate more cuts throughout the field, not just at the edges, which is why they sit at the top of the waste range.
How many tiles are in a box?
It varies by product — anywhere from about 10 tiles for large-format tile to 90 or more for small mosaics. Tiles per box isn't standardized, so check the box label, which lists both the piece count and the square-foot coverage. To find how many boxes you need, divide your total area including waste by the square-foot coverage on the box and round up to whole boxes.
How many boxes of tile do I need?
Divide your total area including the waste allowance by the square-foot coverage printed on the box, then round up to the next whole box. For example, 110 sq ft of coverage with boxes that each cover 15 sq ft needs ceil(110 ÷ 15) = 8 boxes. Always round up — you can't buy a partial box, and the extra becomes your repair stock.
Related calculators
Sources
- Tile CalculatorInch CalculatorCoverage table (tiles per 100 sq ft by size), the area-÷-tile-area formula, and waste guidance: 10% for straight-set, 15–20% for diagonal and patterned layouts.
- How Much Tile Do I Need? Here's How to Calculate ItBob VilaConfirms budgeting up to 20% extra for complex layouts such as herringbone or a diagonal offset, versus about 10% for a standard installation.
- Tile CalculatorOmni CalculatorEffective-tile-size method: grout joint width is added to each tile dimension, so a wider joint means fewer tiles cover the same area.
- How to Calculate Tile Needed for a ShowerFlooring ClarityShower measuring (each wall as height × width plus the pan, niche left in) and waste factors: about 15% for typical work, 20–25% for small tile, mosaics, or diagonal layouts.
- Ceiling Tile CalculatorCeilumeStandard suspended-ceiling tile sizes: 2 × 2 ft (4 sq ft) and 2 × 4 ft (8 sq ft), so room area is divided by 4 or 8 for the grid tile count.