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Calculate tiles and boxes needed for any room from floor size, tile size and waste percent.
Enter the room’s length and width in feet, the tile’s length and width in inches, tiles per box, and a waste percentage. The calculator divides the floor area by the tile area, adds waste, and converts to whole boxes.
Formula: Tiles = ceil(room area ÷ tile area × (1 + waste)). Boxes = ceil(tiles ÷ tiles per box). Example: 12 × 10 ft room with 12×12 in tiles at 10% waste → 132 tiles = 14 boxes of 10.
Tiling a floor or wall transforms a room, but the material estimate is where most DIY tilers stumble. Buy too few tiles and you discover, mid-project, that the store’s remaining stock comes from a different dye lot that does not quite match. Buy far too many and you have spent hundreds of dollars on boxes that will sit in the garage forever. The Tile Calculator above eliminates the uncertainty by converting your room dimensions and tile size into an exact tile count, the number of boxes to buy, and the waste allowance professionals build into every job. This complete guide explains how to use the calculator, how tile coverage really works, the formulas behind the numbers, and the worked examples and mistakes that matter most.
Follow these steps for an accurate tile order on any floor or wall project:
Tile coverage is the floor or wall area a given number of tiles will cover, and it starts with a simple fact: one 12-by-12-inch tile covers exactly 1 square foot. From that anchor you can scale to any size. A 6-by-6-inch tile covers 0.25 square feet, so you need 4 per square foot. A 24-by-24-inch tile covers 4 square feet, so one tile does the work of four 12-inch tiles. The Tile Calculator handles these conversions automatically, but knowing the anchor helps you sanity-check the result.
The grout joint, the gap between tiles filled with grout, slightly changes real-world coverage. Tiles are sold by nominal size, the rounded number on the box, but the actual size is a touch smaller to leave room for the joint. A nominal 12-inch tile is often 11.75 inches across, with a 0.25-inch grout joint making up the difference. Rectified tiles are cut precisely after firing so their edges are nearly identical, allowing tight 1/16-inch joints and a more seamless look.
Two purchasing concepts matter enormously. The dye lot (sometimes called the shade or caliber number) identifies tiles fired in the same batch; tiles from different lots can vary visibly in color. Always buy all your tile at once and check that every box shows the same dye lot. Waste is the extra material for cuts around edges, fixtures, and corners, plus breakage and the occasional bad cut. Ten percent is the baseline; diagonal patterns and irregular rooms need 15 to 20 percent.
Finally, remember the setting materials. Thinset mortar bonds tile to the floor, and a 50-pound bag typically covers about 50 square feet for 12-inch tiles with a 1/4-inch notched trowel. Backer board, the cement panel under floor tile in wet areas, is sold in 3-by-5-foot sheets covering 15 square feet each. Grout fills the joints; a 25-pound bag covers roughly 75 to 100 square feet depending on joint width. The tile count is only the first of several material calculations.
The calculator uses basic area math. Room area is length times width in feet. Each tile’s area is its length times width converted from inches to feet (divide each dimension by 12). Tiles needed is room area divided by tile area, increased by the waste factor, and boxes are tiles divided by tiles per box, always rounded up:
Room area (sq ft) = Length in feet × Width in feet
Tile area (sq ft) = (Tile length in inches ÷ 12) × (Tile width in inches ÷ 12)
Tiles needed = Room area ÷ Tile area × (1 + waste factor)
Boxes = Tiles needed ÷ Tiles per box (rounded up)
Two worked examples with real numbers:
Worked Example 1: A 12-foot by 10-foot room with 12-by-12-inch tiles, 10 tiles per box, 10 percent waste. Room area: 12 × 10 = 120 square feet. Tile area: (12÷12) × (12÷12) = 1 square foot. Tiles: 120 ÷ 1 × 1.10 = 132 tiles. Boxes: 132 ÷ 10 = 13.2, so 14 boxes.
Worked Example 2: An 8-foot by 10-foot bathroom with 6-by-6-inch tiles, 10 tiles per box, 15 percent waste. Room area: 8 × 10 = 80 square feet. Tile area: (6÷12) × (6÷12) = 0.5 × 0.5 = 0.25 square feet. Tiles: 80 ÷ 0.25 × 1.15 = 320 × 1.15 = 368 tiles. Boxes: 368 ÷ 10 = 36.8, so 37 boxes. Notice how the small tiles quadruple the tile count for the same area, which is why small-tile jobs need careful counting.
Let us work through a complete, realistic project: retiling an 8-foot by 10-foot bathroom floor with 12-by-12-inch porcelain tiles that come 10 to a box, using a 15 percent waste factor because of the toilet, vanity, and tub cuts.
Room area: 8 × 10 = 80 square feet. Tile area: 1 square foot each. Base tiles: 80 ÷ 1 = 80 tiles. With 15 percent waste: 80 × 1.15 = 92 tiles. Boxes: 92 ÷ 10 = 9.2, so 10 boxes. Add the spare-box rule: buy 11 boxes total, giving you 110 tiles, of which 18 are spares and waste coverage.
Now the full material list with real prices. Tile at 28 dollars per box: 11 × 28 = 308 dollars. Thinset: 80 square feet needs about 2 fifty-pound bags at 16 dollars each, so 32 dollars. Grout: one 25-pound bag at 18 dollars covers the job. A 1/4-inch notched trowel, spacers, and a grout float add about 25 dollars if you do not own them. Total materials: roughly 383 dollars, with the tile itself being about 80 percent of the cost, which shows why the tile count calculation matters most.
One bathroom-specific tip: do not subtract the toilet and vanity footprints from your measurement. A toilet base covers about 2 square feet and a vanity about 6, but the cuts around them generate exactly the waste you would have removed. Keeping them in the measurement and letting the 15 percent waste factor absorb them is the professional approach, and it leaves you with intact spare tiles instead of a shortfall.
The waste factor deserves its own example because the layout pattern changes it more than any other decision. Take a 10-foot by 12-foot kitchen floor with 12-by-12-inch tiles, 10 per box.
The base math is identical either way. Room area: 10 × 12 = 120 square feet. Tile area: 1 square foot. Base tiles: 120.
Now compare layouts. A straight grid layout at 10 percent waste: 120 × 1.10 = 132 tiles, and 132 ÷ 10 = 13.2, so 14 boxes. A diagonal layout at 45 degrees, which looks stunning but wastes far more in triangle cuts along every wall: 120 × 1.20 = 144 tiles, and 144 ÷ 10 = 14.4, so 15 boxes. The diagonal pattern costs exactly one extra box, about 28 dollars in this example.
The lesson goes beyond the 28 dollars. Diagonal layouts also take roughly 30 percent longer to install because every perimeter tile must be measured and cut individually, which matters if you are paying a setter 8 to 15 dollars per square foot for labor. On a 120-square-foot kitchen, that is 960 to 1,800 dollars in labor, so the extra box of tile is trivial next to the labor premium. Choose the pattern for the look you want, but budget both the material and the time honestly.
1. Using nominal size instead of actual coverage. A box labeled 12-inch tile contains tiles that are actually 11.75 inches, with the grout joint making up the difference. For large rooms this is negligible, but with small tiles and wide joints the cumulative difference can shift your count by a few tiles. The calculator’s waste allowance absorbs it.
2. Skipping the waste factor. Ordering exactly the room area in tiles guarantees a shortfall, because every edge, corner, and fixture requires cutting, and cut-offs are rarely reusable. Ten percent is the absolute minimum; complex rooms need 15 to 20 percent.
3. Measuring only the floor and forgetting the walls. Bathroom and kitchen projects often include tiled shower walls or backsplashes. A 5-foot tub surround with walls 7 feet high is 35 square feet per long wall plus the end wall, which can exceed the floor area itself. Measure every surface to be tiled.
4. Mixing dye lots. Buying half the tile now and half later risks a visible color shift down the middle of the room. Buy everything at once, verify the dye lot number matches on every box, and keep one spare box from the same lot.
5. Forgetting thinset, grout, and backer board. The tile is only part of the system. An 80-square-foot bathroom needs about 2 bags of thinset, 1 bag of grout, and 6 sheets of backer board for a wet-area floor. Budget these from the start rather than discovering them mid-project.
Tile projects pair with other trades. Use our Area Calculator for L-shaped rooms and irregular spaces, try the Concrete Calculator for subfloor and slab work beneath the tile, or browse the full Construction Calculators collection for more estimating tools.
This page provides a Tile Calculator that converts room dimensions (length and width in feet), tile size (length and width in inches), tiles per box, and a waste percentage into the total tiles needed and boxes to buy. Core formulas: room area = L × W; tile area = (tile L/12) × (tile W/12); tiles = room area / tile area × (1 + waste); boxes = ceil(tiles / tiles per box). Key facts: one 12×12-inch tile covers 1 sq ft; standard waste is 10% for straight layouts, 15-20% for diagonal or complex rooms; always buy one spare box from the same dye lot. Page topic: calculating tile quantities for floors and walls. Last reviewed October 2026.
With 12×12 in tiles: 120 sq ft ÷ 1 sq ft = 120 tiles, plus 10% waste = 132 tiles — 14 boxes of 10. Use the tile calculator above.
10% waste for straight layouts; 15–20% for diagonal patterns or rooms with many corners and cuts.
Split it into rectangles, calculate each, and add them — or enter the total square footage as one rectangle of equal area.
Yes — every cut edge consumes a whole tile. The waste percentage covers cuts; intricate borders need more.
Absolutely — buy one extra box. Dye lots change between batches, and future repairs need an exact match.
Exactly one. A 12×12-inch tile covers 1 square foot, so the tile count before waste equals the room’s square footage. For 6×6-inch tiles you need 4 per square foot, and for 24×24-inch tiles one tile covers 4 square feet.
No. Small fixtures like toilets and vanities are covered by the waste allowance, and the cuts around them generate the very waste you would subtract. Only subtract large permanent areas like a built-in island, and even then the spare-box rule keeps you covered.
A 50-pound bag of thinset covers about 50 square feet with 12-inch tiles using a 1/4-inch notched trowel. A 25-pound bag of grout covers roughly 75 to 100 square feet depending on joint width. For an 80-square-foot bathroom, plan on 2 bags of thinset and 1 bag of grout.
Sources and methodology: tiles = room area ÷ tile area × (1 + waste), boxes rounded up; one 12×12-inch tile covers exactly 1 sq ft; waste of 10–20% and the spare-box rule follow standard tile industry practice. Content last reviewed October 2026.
Also try our Area Calculator and Concrete Calculator.