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Tile

How Many Tiles Do You Need

Tile quantity is area, then pieces, then boxes—if you know the carton. The tile calculator shows that working. Waste is the judgment call most tools hide; this site labels the defaults as conventions on purpose.

The math

area_sq_ft = length_ft × width_ft
order_sq_ft = area_sq_ft × (100 + waste%) / 100
tile_face_sq_ft = (width_in × length_in) / 144
pieces = ceil(order_sq_ft ÷ tile_face_sq_ft)

Irregular rooms are sums of rectangles (or a measured net area) before waste. Subtract only openings you will not tile. The calculator’s application modes set different waste defaults; you can still edit the percent.

Waste defaults on this site

None of those numbers are TCNA Handbook tables or manufacturer TDS purchasing yields. They are labeled in tile-waste.json and explained in tile waste factor. Attic stock for future repairs (dye lot) is a different reason to buy extra—do not double-count it on top of cut waste without thinking.

Worked example: 12×10 ft floor, 12×12 in tile

area = 12 × 10 = 120 sq ft

+ 10% waste → order ≈ 132.0 sq ft

12×12 in tile = 1 sq ft each → 132 pieces

Same room with diagonal waste at 20%: order ≈ 144.0 sq ft → 144 pieces. Larger format tile changes piece count more than it changes order square footage; grout volume moves the other way—joint width and tile size dominate grout quantity.

Boxes are optional

Carton coverage is SKU-specific. The calculator lets you enter square feet per box from the label you are holding instead of inventing brand presets. Order square footage and piece count remain the primary outputs so a mismatched carton label cannot silently break the takeoff.

A carton that claims “covers 15 sq ft” is only as good as how that brand measured coverage — some labels assume a nominal size with grout joint already baked in, others are face area only. When the label is ambiguous, order from piece count and confirm boxes at the aisle: pieces per box times face area should land near the order square footage you already trust.

Floor versus wall versus diagonal

Floors are usually the simplest plane: one rectangle, fewer obstacles, waste starting at 10%. Walls and showers multiply cut edges — niches, benches, curbs, valve plates — so the tool starts waste at 15%. For a full surround (three walls plus optional floor, ceiling, and niche), use the shower tile calculator. Diagonal and patterned layouts burn more perimeter scrap; the diagonal default is 20%. None of those starting points are sacred. If you chalked a herringbone dry layout and already see a pile of triangles, raise the percent before you buy.

Backsplashes behave like short walls with lots of outlets. Treat them as wall/shower waste unless the field is a single clean rectangle with almost no cuts. Large-format tile on a floor can still want more than 10% if the room is out of square and every edge needs a taper — waste is about the cutting plan you will actually execute, not the room’s marketing photo.

Measuring irregular rooms

L-shaped kitchens and baths are sums of rectangles. Measure each rectangle, add the areas, then apply waste once to the total — do not apply waste to each bay and then pad again. Subtract only openings you will not tile (a tub deck you are leaving bare, a large window you are stopping under). Do not subtract every doorway threshold if you are still setting tile through it.

When walls are out of square, the calculator still wants a net area. Walk the perimeter with a laser or tape, sketch the odd corners, and prefer over-measuring slightly to inventing a perfect rectangle that never existed. The waste field is the honest place for layout risk; inflating length and width “for luck” on top of a high waste percent is how orphan cartons happen.

Piece size changes the shopping list

Order square footage is mostly indifferent to tile size; piece count is not. A 120 sq ft order is about 120 pieces of 12×12, about 30 pieces of 24×24 (each 4 sq ft), and hundreds of mosaic faces if you are counting individual tesserae instead of sheet area. Enter the face size you are buying — mosaic sheet face area if the sheet is sold as a unit — so piece count matches the SKU on the shelf.

Rectified large-format tile often wants tighter joints and more careful layout. That does not change the area formula, but it can change how much waste you should carry because a single bad cut is expensive. Raise waste when the tile is brittle, expensive to replace, or dye-lot sensitive.

What changes the answer

Run your dimensions in the tile calculator, then the grout calculator with the joint you will actually tool. Sourcing rules: methodology.

Frequently asked questions

How do I calculate how many tiles I need?

Measure net area (length × width for a rectangle), multiply by (1 + waste%/100) for order square footage, then divide by the face area of one tile and round up. Boxes are optional once you know sq ft per carton.

What waste percent should I use for floor tile?

This site’s floor straight-layout default is 10% — a labeled trade convention for cuts and breakage, not a TCNA Handbook table or manufacturer TDS yield. Walls/showers default to 15%; diagonal/pattern to 20%.

How many 12×12 tiles for a 12×10 room?

Area = 120 sq ft. With 10% floor waste, order ≈ 132.0 sq ft. At 1 sq ft per 12×12 tile that is 132 tiles before you convert to boxes from your carton label.

Does the calculator include thinset and grout?

Tile count and order area are separate from grout. Use the grout calculator with your tile size and joint width; thinset stays out of scope until product coverage is sourced.

Why won’t you cite TCNA for waste?

We do not have a TCNA Handbook table or manufacturer TDS that publishes these exact defaults as purchasing yields. Dressing a convention up as a standard would be dishonest—see the waste-factor guide.