Tile Calculator
Calculate how many tiles and boxes you need for a floor or wall, with built-in waste allowance for cuts and breakage.
What is Tile Calculator?
The tile calculator counts exactly how many tiles and boxes you need for a floor or wall project, including a waste allowance for cuts at the edges and the occasional cracked piece. Perfect for planning bathroom floors, kitchen backsplashes, entryways, and shower surrounds.
Formula
Area of room (in square inches) = length(ft) × 12 × width(ft) × 12
Area of each tile = tileL × tileW (inches)
Tiles needed = ⌈(room area ÷ tile area) × (1 + waste %)⌉
Standard waste allowances: 10% for rectangular rooms with simple cuts, 15% for rooms with angles or niches, 20% for diagonal installations.
Worked example
A 10' × 8' bathroom with 12" × 12" tiles, 10% waste, 10 tiles per box:
- Room area = 120" × 96" = 11,520 sq in
- Tile area = 144 sq in
- Tiles = ⌈(11,520 / 144) × 1.10⌉ = ⌈88⌉ = 88 tiles
- Boxes = ⌈88 / 10⌉ = 9 boxes
How to use this calculator
- Measure the room length and width in feet. For irregular rooms, break into rectangles and sum.
- Enter the nominal tile size in inches (sold as "12×12," "6×24," "3×6 subway," etc.).
- Keep the default 10% waste for straight layouts; bump to 15–20% for diagonal or pattern layouts.
- Check the box label for tiles-per-box and unit price.
Always buy one extra box from the same dye lot — future repairs are nearly impossible to match from different batches.
Frequently asked questions
Why do I need waste allowance?
Edge tiles must be cut to fit, and the cut-off portions are usually too small to reuse. A few tiles inevitably crack during handling or installation. For a simple 10' × 8' rectangular room, 10% is enough. For diagonal installs, herringbone patterns, or rooms with many angles/columns, 15–20% is safer.
What size tile is best?
Large tiles (12×24, 18×18) make small rooms look larger and mean fewer grout lines (easier cleaning). Smaller tiles (6×6, mosaic) grip better on sloped shower floors and are more forgiving on uneven substrates.
How much thinset and grout will I need?
Roughly one 50-lb bag of thinset covers 40–70 sq ft depending on tile size and trowel notch. One 25-lb bag of sanded grout covers about 100 sq ft for 12×12 tiles with 1/4" joints. Always check the bag for specifics.
Can I tile directly over existing tile?
Sometimes — if the existing tile is solid, flat, and well-bonded, you can use a bonding primer and tile over it. But the floor gets thicker (which can affect doors and transitions), and any loose tile underneath will eventually cause a crack above. When in doubt, tear out.