Calculators
Tile calculators
Floor tile, wall tile, backsplashes and showers, with the grout, thinset, backer board and spacers to go with them.
Tile is sold by the box and the box is labelled in square feet, so every tile estimate starts with an area and ends with a whole number of boxes. In between sit the three things that change the answer: the size of the tile with its grout joint, the layout you have chosen, and how many cuts that layout forces along the walls. A straight grid in a square room wastes little; the same tile set on the diagonal wastes half as much again, and a herringbone of narrow planks wastes more still.
These calculators keep those parts separate. Each one shows the area, the tiles before waste, the allowance you picked and the boxes it becomes, so you can see which number to argue with. The grout and mortar tools work from the same tile size and joint width, because a wider joint takes more grout and a larger tile takes a bigger trowel notch, and the layout tool tells you before you open a box whether the last row will be a sliver.
9 calculators
Floor Tile Calculator
Tiles and boxes for a floor from the room size, the tile size, the grout joint and the layout.
Wall Tile Calculator
Tiles and boxes for up to four walls, less the doors and windows, by tile size and layout.
Backsplash Tile Calculator
Tiles or mosaic sheets for a kitchen backsplash, less the window and outlets, plus the edge trim.
Shower Tile Calculator
Wall tile boxes, floor mosaic sheets and bullnose trim for a three-wall shower with a niche.
Grout Calculator
Pounds and bags of grout from the tile size, thickness, joint width and grout type.
Thinset Mortar Calculator
Bags of thinset from the area and the trowel notch, with back-buttering for large tile.
Cement Backer Board Calculator
Sheets of cement board, the screws, the mesh tape and the thinset to bed it, for a floor or a wall.
Tile Layout Calculator
Full tiles per row, the cut widths at each wall, and whether to centre a tile or a joint to avoid slivers.
Tile Spacers & Leveling Clips Calculator
Spacers by pattern, leveling clips by tile size and wedges, in bags, from the tile count.
Guides for this topic
Flooring waste factors: 5%, 10%, 15% or 20%?
The right waste allowance is the one that matches your layout and room, not the one everybody repeats. Here is where 10, 15 and 20% come from, and the adjustments that move them.
How much flooring do I need? The complete method
Measure the room in rectangles, add the waste your layout demands, divide by what the box really covers, round up once, and count the trim. Here is each step, with a living room worked from start to finish.
Large-format tile: what it needs before you order
Big tiles look clean and save grout, but they need a flatter floor, deeper mortar, leveling clips and careful layout. Here is what changes in the order and on the floor when a tile side reaches 15 inches.
Electric radiant floor heating: area, watts, circuit and running cost
Electric floor heat is sized by the open floor you stand on, not the room. Here is how to work out the heated area, the load on the circuit and the monthly bill for a bathroom and a kitchen.
Thinset coverage by trowel size: how many bags of mortar?
The notch on the trowel decides how much mortar goes under each square foot, and so how many bags you need. A floor of large tile can take three times the mortar of the same floor in small tile.
Tile size, grout joint and what they do to your quantities
A tile and its joint decide almost every other number on a tile job. Bigger tiles mean fewer joints and less grout but a flatter floor and more mortar; wider joints mean fewer tiles but much more grout.
Tiling a shower: every quantity, from walls to the floor
A shower is three walls, a floor, a niche, a curb and a lot of edges. Each has its own quantity, and the edges are the one people forget. Here is the whole list for a standard alcove.
Questions people ask
- How many boxes of 12 × 24 tile do I need for 150 square feet?
- With a 1/8 inch joint and a straight layout, 150 sq ft plus 10% waste is 165 sq ft. At 16 sq ft per box that is 10.3 boxes, so you buy 11 and have about 11 sq ft spare. Set on the diagonal the allowance rises to 15%, which is still 11 boxes here but tips to 12 in a slightly larger room.
- How much extra tile should I buy for a diagonal layout?
- Plan on 15% over the measured area for a 45-degree layout, against 10% for a straight grid. Every wall gets a run of triangular offcuts and most of them cannot be reused, and a room with alcoves, a bay or several doorways is closer to 18 to 20%.
- How much grout do I need per square foot?
- It depends on the joint and the tile. A 12 × 12 inch tile with a 1/8 inch joint set 3/8 inch thick takes about 0.08 lb of sanded grout per sq ft, so a 25 lb bag covers roughly 320 sq ft. Halve the tile size or double the joint width and the grout roughly doubles. The grout calculator does the exact arithmetic from your tile dimensions.
- How many bags of thinset for a floor?
- A 50 lb bag of modified thinset covers roughly 90 to 100 sq ft with a 1/4 inch square-notch trowel, 60 to 70 sq ft with a 1/4 × 3/8 inch notch, and 40 to 50 sq ft with a 1/2 inch notch. Large tiles need the bigger notch and often back-buttering, which can double the mortar. A 150 sq ft floor of 12 × 24 tile usually takes three bags.
- How many sheets of cement board for a bathroom floor?
- Divide the floor area by the sheet area and round up, then add about 10% for cuts around the toilet flange and the door. A 3 × 5 ft sheet is 15 sq ft, so a 40 sq ft bathroom floor needs 3 sheets; a 4 × 8 ft sheet is 32 sq ft and the same floor needs 2. Each sheet also needs a bed of thinset under it and about 30 to 40 screws.
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