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Construction & Home
Tile Calculator — How Many Tiles & Boxes You Need
How many tiles and boxes you need for a floor, wall, backsplash or shower
A tile calculator turns a room's dimensions and a single tile's size into the one number that matters at the store: how many tiles to buy. Whether you're laying a kitchen floor, a bathroom wall, a shower surround or a backsplash, the math is the same — find the area to cover, find the area each tile covers, divide, and add extra for cuts and breakage.
The core formula is Tiles = ceil( area ÷ tile area × (1 + waste) ). First get the room area in square feet: area = length × width. A floor that's 10 ft by 10 ft is 100 sq ft. Then get the area of one tile. Tile sizes are quoted in inches, so a 12 × 12 in tile covers (12 × 12) ÷ 144 = 1 sq ft — there are 144 square inches in a square foot. A 100 sq ft floor therefore needs 100 ÷ 1 = 100 tiles before waste, and 110 tiles with the standard 10% allowance.
The waste factor is the part beginners skip. Tiles snap, blades chip corners, and every edge against a wall needs a cut that wastes part of a tile. A good rule of thumb:
• 10% for a simple square or rectangular room with a straight (grid) layout. • 15% for a diagonal layout, lots of corners, or a small busy room like a bathroom. • 20% for diagonal large-format tile or a herringbone / complex pattern, where offcuts are rarely reusable.
The other real-world wrinkle is that tile is sold by the box, not the tile. A box might hold 6, 10 or 12 tiles. You can't buy a partial box, so the calculator divides your tile count by the tiles-per-box and rounds up — buying 11 boxes of 10 to get the 105 tiles you need. Keeping a spare box sealed is smart anyway: dye lots change between production runs, so a tile bought next year to fix a crack rarely matches.
This tool reports the floor area, the area each tile covers, the raw tile count, the count with waste added, the number of full boxes to purchase, and — if you enter a price per tile or per box — the total material cost. Every quantity is rounded up to a whole purchasable unit, because you can't lay 104.3 tiles or open two-thirds of a box.
📖 See also: How to Calculate a Tip (and Split the Bill)
Calculator
Fill in the fields and click "Calculate" for instant results.
📰 Formula
• Room area (sq ft) = length (ft) × width (ft) • Tile area (sq ft) = (tile width in × tile height in) ÷ 144 • Tiles needed = ceil( area ÷ tile area × (1 + waste/100) ) • Boxes needed = ceil( tiles ÷ tiles per box ) • Total cost = tiles × price per tile (or boxes × price per box) Material constants: • 144 square inches = 1 square foot • Default waste allowance = 10% (use 15% for diagonal/small rooms, 20% for herringbone/large-format diagonal) • A 12 × 12 in tile = 1.0 sq ft; an 18 × 18 in tile = 2.25 sq ft; a 6 × 24 in plank tile = 1.0 sq ft
📰 Formula
• Room area (sq ft) = length (ft) × width (ft) • Tile area (sq ft) = (tile width in × tile height in) ÷ 144 • Tiles needed = ceil( area ÷ tile area × (1 + waste/100) ) • Boxes needed = ceil( tiles ÷ tiles per box ) • Total cost = tiles × price per tile (or boxes × price per box) Material constants: • 144 square inches = 1 square foot • Default waste allowance = 10% (use 15% for diagonal/small rooms, 20% for herringbone/large-format diagonal) • A 12 × 12 in tile = 1.0 sq ft; an 18 × 18 in tile = 2.25 sq ft; a 6 × 24 in plank tile = 1.0 sq ft
🧪 Worked examples
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Example 2
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Example 3
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Example 4
⚠️ Common mistakes
- Forgetting to divide tile inches by 144 — using 12 × 12 = 144 sq ft per tile instead of 1 sq ft.
- Skipping the waste percentage, so the first broken tile or wall cut leaves you short.
- Mixing feet and inches — entering the room in feet but the tile in feet too, or vice versa.
- Rounding tiles or boxes down instead of up (you can't buy a fraction of a box).
- Using a 10% allowance for a diagonal or herringbone layout that really needs 15–20%.
💡 Tips
- Always round up to whole tiles and whole boxes — partial units aren't sold.
- Buy one extra sealed box and keep it for future repairs; dye lots shift between batches.
- Use 15% waste for bathrooms and diagonal layouts, 20% for herringbone or large-format diagonal.
- Measure each wall or floor section separately, then add the areas before dividing by tile size.
- Subtract large openings (a big window or a built-in tub) only if they exceed ~25 sq ft — otherwise leave them in as extra waste cushion.
Embed this calculator on your site
Copy the code below and paste it into the HTML of your site or blog.
<iframe src="https://www.calcnimbus.com/embed/tile-calculator" width="100%" height="500" frameborder="0" style="border:1px solid #eee;border-radius:12px"></iframe>
❓ Frequently asked questions
How do I calculate how many tiles I need?
Find the area to cover in square feet (length × width), find the area of one tile ((tile width × tile height) ÷ 144), then divide and add waste. Tiles = ceil(area ÷ tile area × 1.10) for a 10% allowance.
How many 12x12 tiles do I need for 100 square feet?
A 12 × 12 in tile is exactly 1 sq ft, so 100 sq ft needs 100 tiles before waste. With the standard 10% allowance for cuts and breakage, buy 110 tiles.
What waste percentage should I use for tile?
Use about 10% for a straight grid layout in a simple rectangular room. Bump it to 15% for diagonal layouts or small busy rooms, and 20% for herringbone or large-format diagonal where offcuts can't be reused.
How do I figure out how many boxes of tile to buy?
Divide your total tile count (with waste added) by the number of tiles in a box, then round up. If you need 105 tiles and a box holds 10, that's ceil(105 ÷ 10) = 11 boxes.
How do I calculate tiles for a backsplash or wall?
It's the same math as a floor: measure the wall area in square feet (height × width), divide by the tile area in square feet, and add waste. A 30 sq ft backsplash in 3 × 6 in subway tiles needs about 264 tiles at 10% waste.
Should I subtract doorways, windows, or a tub from the area?
Subtract only large openings — roughly 25 sq ft or more, like a big picture window or a built-in tub. Small gaps are better left in as extra cushion, since you lose tile to cuts around them anyway.
How many square inches are in a square foot for tile math?
There are 144 square inches in one square foot (12 × 12). That's why you divide a tile's inch dimensions by 144 to get its area in square feet. A 12 × 12 in tile is 144 ÷ 144 = 1 sq ft.
Is a tile calculator different from a flooring calculator?
Yes. A tile calculator counts individual tiles (and boxes of tiles) from a tile's inch dimensions. A flooring calculator usually works in boxes of plank that each cover a known square footage, so you compare areas rather than counting pieces.
Why round up instead of using the exact tile count?
Because you can't buy a fraction of a tile or open part of a box, and you need spares for breakage and future repairs. Rounding up to whole tiles and whole boxes guarantees you finish the job without a second trip.