Introduction
Tile jobs come down to arithmetic that’s easy to get wrong. A 12 ft × 10 ft room at 120 square feet. A 12-inch tile with a 1/8-inch grout line covers a bit more than one square foot once you account for the joint. So the count isn’t 120 tiles. It’s closer to 110. Add 10% waste and you’re at 121. Buy in boxes of 10 and you’re ordering 130 tiles. That’s the real order, and it’s not the number most people land on with a pad and pencil.
The calculator handles the grout-line adjustment for you. That’s the piece most people skip. It also multiplies through to boxes, so you walk into the store knowing how many cases to pull, not just how many loose tiles.
Pricing options cover the common ways tile is sold. Some shops quote per tile, some per box, some per square foot. Pick the unit your supplier uses and the tool converts it internally.
How to Use the Tile Calculator
Pick the currency from the dropdown if your supplier doesn’t quote in US dollars.
Enter the room length and select the unit: feet, inches, yards, meters, centimeters, or millimeters.
Enter the room width and pick its unit.
Enter the tile length and pick the unit.
Enter the tile width and pick its unit.
Enter the grout line width. One-eighth inch is standard for most floor tile. Large-format tile often uses 3/16 or 1/4 inch.
Set the waste factor. Ten percent is safe for a straight-lay room. Bump it to 15% for diagonal patterns or rooms with lots of cuts.
Enter how many tiles come in a box.
Type in the price per tile. Switch the dropdown to per box, per square foot, or per square meter if that’s how your supplier quotes.
Add any adhesive, grout, or underlayment cost as a flat total.
Hit Calculate. The Summary tab shows the headline numbers. The Detailed Breakdown tab walks through every conversion.
How the Tile Calculator Formula Works
The tool converts room and tile dimensions to feet, then calculates in square feet.
Formula: Room Area (ft²) = Room Length (ft) × Room Width (ft)
Formula: Tile Area with Grout (ft²) = (Tile Length + Grout) × (Tile Width + Grout)
Formula: Tiles Needed = ceil(Room Area ÷ Tile Area with Grout)
Formula: Tiles with Waste = ceil(Tiles Needed × (1 + Waste % ÷ 100))
Formula: Boxes Needed = ceil(Tiles with Waste ÷ Tiles per Box)
Formula: Total Tiles to Purchase = Boxes Needed × Tiles per Box
Formula: Tile Cost = Total Tiles × Price per Tile
Formula: Total Cost = Tile Cost + Additional Cost
The grout adjustment is what separates this from a plain area calculator. A 12-inch tile with a 1/8-inch joint has an effective footprint of 12.125 inches, or roughly 1.021 square feet. That’s 2% more coverage per tile than the tile itself provides. Ignore it and you over-order. On a 500 square foot floor, that’s 10 tiles you didn’t need.
The tiles-needed count rounds up. A room that needs 118.3 tiles becomes 119. Then waste applies. Then boxes round up. If 130 tiles are needed and boxes hold 10, you buy 13 boxes, which is 130 tiles exactly. If boxes hold 12, you buy 11 boxes, which is 132 tiles. That’s the practical cost of box sizing.
Price conversions run internally. Per box divides by tiles-per-box to get per tile. Per square foot multiplies by the tile’s effective area. Per square meter multiplies by the effective area in square meters. Whatever unit you enter, the final cost multiplies the total tiles purchased by the per-tile equivalent.
Worked Example
You’re tiling a 14 ft × 11 ft kitchen floor. The tile is 18 inches by 18 inches. Grout lines are 3/16 inch. Waste is 10% for cuts around cabinets and the doorway. Boxes hold 8 tiles. Your supplier charges $3.85 per tile, and you’re adding $220 for thinset, grout, and spacers.
Step 1: Convert to feet.
Tile length: 18 ÷ 12 = 1.5 ft. Tile width: 1.5 ft.
Grout: 0.1875 ÷ 12 = 0.015625 ft.
Step 2: Room area.
14 × 11 = 154 ft².
In square meters: 154 × 0.092903 = 14.31 m².
Step 3: Effective tile area.
(1.5 + 0.015625) × (1.5 + 0.015625) = 1.515625 × 1.515625 = 2.2971 ft².
Step 4: Tiles needed.
ceil(154 ÷ 2.2971) = ceil(67.04) = 68 tiles.
Step 5: Add 10% waste.
ceil(68 × 1.10) = ceil(74.8) = 75 tiles.
Step 6: Boxes needed.
ceil(75 ÷ 8) = ceil(9.375) = 10 boxes.
Step 7: Total tiles to purchase.
10 × 8 = 80 tiles.
Step 8: Tile cost.
80 × $3.85 = $308.00.
Step 9: Total cost.
$308.00 + $220.00 = $528.00.
The Summary tab reads: room area 154 ft² (14.31 m²), tile area with grout 2.2971 ft² (0.2134 m²), 68 tiles needed, 75 with waste, 10 boxes, 80 total tiles to purchase, $308.00 tile cost, $528.00 total cost. The breakdown tab lists the grout width in feet, the effective tile dimensions, and each cost line.
Switch to 24-inch tile and the count drops. Effective area becomes 4.016 square feet per tile. Tiles needed falls to 39, and the order drops to 6 boxes of 8, or 48 tiles. Same floor, larger tile, fewer pieces.
