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Backsplash Tile Calculator

Use this free backsplash tile calculator to work out exactly how much tile to buy for your kitchen or bathroom backsplash. Enter the wall length and height, pick your tile size — subway, square, mosaic, or large format — and the calculator gives you the tiles needed, the boxes to buy, and a grout estimate, with the waste allowance already included so you never run short mid-job.

How it works

The calculation has three steps. First, the wall area: multiply the wall length by the height. A wall 20 feet long and 1.5 feet high is 30 square feet. If your backsplash runs along two walls, measure each run separately and add the areas together, and subtract the area of any window, range hood, or other opening that will not be tiled. Second, divide the wall area by the area of one tile. A 3 by 6 inch subway tile covers 18 square inches, which is 0.125 square feet, so 30 ÷ 0.125 = 240 tiles before waste. Third, add the waste allowance: multiply by one plus the waste percentage. At 10 percent waste, 240 × 1.10 = 264 tiles.

Waste is the part people most often skip, and it is the reason so many tiling jobs stall halfway through. Tiles are cut at the edges, around outlets, and at corners, and every cut throws away part of a tile. Five percent is enough for large tiles on a simple straight wall with few cuts. Ten percent is the standard allowance for a normal kitchen backsplash, and it is the default here. Fifteen percent is right for subway tile, walls with many outlets, or diagonal patterns, and herringbone or mosaic work needs 15 to 20 percent because the pattern wastes more material at every edge. It is always cheaper to buy a few extra tiles than to run out and find your batch is sold out.

Boxes are the number you actually buy, and the calculator rounds up to whole boxes: 264 tiles at 40 tiles per box is 6.6 boxes, so you buy 7. Keep one spare box after the job is done. Tiles from a different dye lot can look slightly different, and a spare box lets you replace a cracked tile years later without hunting for a discontinued batch. The grout estimate is based on a 25-pound bag covering roughly 100 square feet of backsplash with standard 1/8-inch joints, so a 30 square foot backsplash needs about one bag. Small mosaic tiles with many joints use more grout, and wide 1/4-inch joints use more too, so buy an extra bag if your tiles are smaller than 2 inches or your joints are wide.

Measuring is where the job is won or lost. Measure the length of each wall run in feet, and the height from the countertop to the bottom of the upper cabinets — usually 18 inches, or 1.5 feet, in a kitchen. In a bathroom the backsplash is often just 4 to 6 inches high behind a vanity, while a full-height backsplash behind a stove can run to the ceiling. Measure twice, in two places, because walls are rarely perfectly straight: if the height differs from one end to the other, use the larger measurement so you do not come up short.

Worked example

You are tiling a kitchen backsplash wall 20 feet long and 1.5 feet high with 3 by 6 inch subway tiles, using a 10 percent waste allowance and buying tiles in boxes of 40.

Step 1: Wall area — 20 × 1.5 = 30 square feet.
Step 2: One tile — 3 × 6 = 18 square inches, which is 18 ÷ 144 = 0.125 square feet.
Step 3: Tiles before waste — 30 ÷ 0.125 = 240 tiles.
Step 4: Tiles with waste — 240 × 1.10 = 264 tiles.
Step 5: Boxes — 264 ÷ 40 = 6.6, rounded up to 7 boxes.
Step 6: Grout — 30 square feet ÷ 100 per bag = 0.3 bags, so buy 1 bag.

The result is 264 tiles, 7 boxes, and 1 bag of grout. If the same wall used 12 by 12 inch tiles instead, it would need only 30 tiles before waste and 33 with waste, but the cuts around outlets would still call for the same 10 percent allowance.

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