How this calculator works
It multiplies the wall length by the height you are tiling, subtracts windows and other openings, adds a cut allowance and divides by the size of one tile. Then it rounds up to whole boxes from the coverage on the box label.
Thinset follows the trowel notch a tile that size usually needs (published bag-chart coverage, conservative end), and grout follows the volume of the joints. Edge trim covers the top edge and both ends of the tiled area in standard lengths.
tile area = wall length × height − openings
tiles = tile area × (1 + cut allowance) ÷ area of one tile
boxes = tiles × area of one tile ÷ box coverage
grout lb = area × 144 × (L + W) ÷ (L × W) × joint × depth × 0.065 × 1.1
edge trim = wall length + 2 × height, in 8 ft lengthsWorked example
A 10′ run of backsplash, 18″ tall, is 15 sq ft. With 3″ × 6″ subway tile (0.125 sq ft each) and 10% for cuts, you need 132 tiles. At 10 sq ft per box that is 1.65 boxes, so you buy 2. A ¼″ × ¼″ notch uses about 9.2 lb of thinset, one 25 lb bag, and 1/16″ joints take about 1.5 lb of grout, one 10 lb bag of unsanded grout. The top edge and both ends add up to 13 ft of trim: two 8 ft lengths.
Tips before you buy
- Measure the backsplash run on the wall, not the countertop, and subtract the range hood or window only if it is large.
- Outlets and switches are not worth subtracting; you need the tile around them anyway.
- In showers and other wet areas, set tile with cement thinset over a waterproofed backer board, not premixed adhesive.
- Buy all the tile from the same lot and keep a few spares for repairs.
Questions
- How much extra wall tile should I buy?
- Plan on about 10% for cuts on a simple wall. Add more for diagonal or herringbone patterns, many outlets and corners, or handmade tile with a lot of variation that you may want to sort.
- Can I use premixed adhesive instead of thinset?
- Premixed tile adhesive (mastic) is made for small tiles on dry walls such as kitchen backsplashes. It is not meant for showers, floors or large tile; use a cement thinset there. Check the coverage chart on the pail if you choose it.
- Do I need sanded or unsanded grout for a backsplash?
- Joints narrower than ⅛″, which are common with subway and ceramic wall tile, take unsanded grout. Joints of ⅛″ and wider take sanded grout because the sand keeps the joint from shrinking and cracking.
- What is edge trim for?
- Most wall tile has an unglazed edge. Where the tiled area stops in the open, a metal or plastic trim strip (or bullnose tile) gives a finished edge. Skip it where the tile runs into a cabinet or a corner.