How to calculate how many tiles you need
The core calculation is simple: divide the area you're covering by the area of a single tile. The two things people miss are units and waste. Tile dimensions are in inches while rooms are measured in feet, so the sizes have to be reconciled — this calculator does that — and then a waste allowance is added on top, because cuts at the edges, the occasional cracked tile, and pattern layouts all consume extra.
Tile calculation formula
Surface area ÷ area of one tile × waste allowance = tiles needed. A 10-by-12-foot room has 120 square feet. With 12-by-12-inch tiles and 10% waste, you should plan for 132 tiles: 120 ÷ 1 × 1.10 = 132.
Floors, walls and backsplashes
For a floor, multiply room length by width. For a wall or backsplash, multiply width by height for each section and add the sections together. You may subtract large doors, windows or cabinet openings, but keeping small openings in the total provides useful extra material for cuts.
How much waste should I add?
For a straight, grid layout in a simple rectangular room, 10% is usually enough. Step up to 15% when there are several cuts around fixtures, and 20% for diagonal or herringbone patterns and rooms with lots of corners. It's cheaper to have a few spare tiles than to run short and risk a batch that doesn't match.
Buying by the box
Tiles ship in boxes, and color can vary slightly between production batches. Order whole boxes from a single batch, and grab one extra for repairs down the road — discontinued lines are impossible to match later.
Frequently asked questions
Does tile size change how many I need?
Yes. Larger tiles cover more area each, so you need fewer of them — but they also produce bigger offcuts at the edges. The calculator accounts for the exact tile size you enter.
What about the grout lines?
Standard grout joints are thin enough that they don't meaningfully change the tile count, and the waste allowance absorbs any difference.
Can I use this for walls?
Yes — enter the wall area instead of the floor area. For a backsplash or shower, measure each wall section and add them together, then subtract large openings if you like.
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