Backsplash Tile Calculator
Figure out the tile and number of boxes for a kitchen backsplash from the counter run and backsplash height, with a waste allowance built in.
How it works
Area = length × (height ÷ 12) · Tiles = ⌈area × (1 + waste%) ÷ tile face area⌉ · Boxes = ⌈tiles ÷ tiles-per-box⌉
A backsplash area is just the counter run length times the backsplash height (converted to feet), so an 18-inch backsplash over a 12-foot run is 18 square feet. Divide by the tile face area for the raw count, add 10% for cuts around outlets and end cuts, then round up to whole boxes because tile is sold by the box. For heavy mosaic sheets, count sheets the same way using the sheet’s coverage.
Worked example
A 12 ft counter run with an 18" backsplash is 12 × 1.5 = 18 sq ft. With 10% waste that is 19.8 sq ft; in 3"×6" subway (0.125 sq ft each) that is about 159 tiles, or 4 boxes of 40.
Frequently asked questions
How tall is a standard backsplash?
The classic full backsplash fills the 18 inches between the countertop and the bottom of the upper cabinets. A short "splash guard" of 4 inches is also common where there are no uppers, and full-height slabs run to the ceiling behind a range.
Do I subtract outlets and windows?
For small outlets it is safer not to — you still buy the tile and cut it, and the offcuts rarely reuse cleanly. Subtract only large openings like a window, and keep the waste allowance to cover the cuts you do make.
Should I buy extra tile?
Yes. Beyond the waste percentage, keep a few spare tiles from the same box for future repairs, since a later purchase may come from a different dye lot with a slightly different shade.
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This calculator is for educational purposes. Double-check important results before acting on them.