What Is the Tile Calculator?
The Tile Calculator works out how many individual tiles are needed to cover a floor, wall or backsplash. It uses the dimensions of the area, the dimensions of a single tile and the width of the grout joint between tiles, then adds a waste allowance for cuts and breakage.
Tile is different from plank flooring because the joints are part of the surface. A grid of 12 inch tiles with a 3/16 inch joint covers slightly more area per tile than the tile’s own face. On a large floor this difference adds up to several tiles, and with small mosaic tiles it is significant.
How the Calculator Works
The calculator multiplies the area’s length and width to get square feet. It then builds a tile module, which is one tile plus one grout joint in each direction. A 12 inch tile with a 1/8 inch joint has a module of 12.125 by 12.125 inches.
The module area in square inches is divided by 144 to convert it to square feet. Dividing the total area by the module area gives the number of tiles needed with no waste. The waste percentage is applied and the result is rounded up to a whole tile.
The Tile Formula
Area = Length × Width
Tile module (sq ft) = (Tile length + Joint) × (Tile width + Joint) ÷ 144
Tiles = Area ÷ Tile module × (1 + Waste % ÷ 100), rounded up
Nominal and actual tile sizes
A tile sold as 12 by 12 inches often measures 11.75 inches or 11.81 inches, which is 300 millimeters. Use the actual size from the product specification where you can. The calculator accepts inches, centimeters and millimeters.
Step-by-Step Explanation
- Measure the length and width of the surface in feet and multiply them.
- Add the grout joint width to the tile length and to the tile width.
- Multiply those two figures and divide by 144 to get the module in square feet.
- Divide the surface area by the module to get the net tile count.
- Multiply by one plus the waste percentage.
- Round up to the next whole tile, then up to whole boxes.
Worked Example
A bathroom floor is 12 feet by 10 feet. The tile is 12 by 12 inches with a 1/8 inch grout joint, laid straight.
- Area: 12 × 10 = 120 square feet.
- Module: 12.125 × 12.125 = 147.02 square inches.
- Module in square feet: 147.02 ÷ 144 = 1.021.
- Net tiles: 120 ÷ 1.021 = 117.5, so 118 tiles.
- With 10 percent waste: 117.5 × 1.10 = 129.3, so 130 tiles.
If the tile comes 10 to a box, you need 13 boxes. For a kitchen backsplash 10 feet long and 18 inches high using 3 by 6 inch subway tile with a 1/16 inch joint, the area is 15 square feet and the module is 0.129 square feet. That gives 116 tiles, or 128 with 10 percent waste.
How to Use the Calculator
- Enter the length and width of the surface to be tiled.
- Enter the length and width of one tile. Switch units to centimeters or millimeters if the tile is metric.
- Enter the grout joint width. Use 0 for butt-jointed tile.
- Choose a waste allowance for your layout.
- Press Calculate to see the tile count and tiles per square foot.
- Divide by tiles per box and round up.
For a room with several sections, total the area first with the Square Footage Calculator. If you are weighing tile against plank, the Flooring Calculator gives box counts for the same room. Outdoor surfaces use the same logic with thicker units, covered by the Paver Calculator. Tiled shower walls need backer board, which you can estimate with the Drywall Calculator since sheet sizes are similar, and the Mortar Calculator helps with setting materials for masonry.
Practical Tips
- Dry-lay a row of tiles in each direction from the centre of the room before mixing any adhesive. Adjust the starting point so edge cuts are at least half a tile.
- Buy all tile from one batch. Shade and calibre numbers are printed on the box and should match.
- Use spacers. They keep joints uniform and make the calculated count accurate.
- Large format tiles need a flatter substrate. Check with a straightedge and level low spots first.
- Order bullnose, trim pieces and thresholds separately. They are counted by length, not area.
- Seal natural stone and cement-based grout after it cures.
- Keep a few spare tiles. A cracked tile five years from now will be hard to match.
Common Mistakes
Ignoring the grout joint. For small tiles, leaving out the joint can overstate the count by 5 percent or more.
Using nominal size. A nominal 12 inch tile that is actually 11.75 inches changes the count across a large floor.
Too little waste on diagonal layouts. Every edge tile is cut on a diagonal, and offcuts are rarely reusable. Use 15 percent.
Not accounting for pattern or veining. Tiles with directional veining or a printed pattern may need to be laid in a set orientation, which increases waste.
Forgetting niches, window returns and steps. These small surfaces add area and a high proportion of cuts.
Rounding to boxes before adding waste. Add waste first, then round to whole boxes.
Choosing a Grout Joint Width
Rectified tiles with precise edges can be set with joints as narrow as 1/16 inch. Standard pressed tiles need 1/8 to 3/16 inch to absorb size variation. Handmade and rustic tiles look right with 1/4 inch or more. Outdoor tile and stone often use 3/8 inch. Narrow joints look sleek but demand a flat substrate and consistent tile.
Thinset and Grout Quantities
Adhesive coverage depends on trowel notch size. A 1/4 inch square notch covers roughly 90 square feet per 50 pound bag, and a 1/2 inch notch covers about half that. Grout quantity depends on tile size, joint width and tile thickness. Small tiles with wide joints use far more grout than large tiles with narrow joints. Manufacturers publish coverage charts, and it is worth checking them once you know your tile count.
Estimating for Different Layouts
Offset or brick pattern
Rows are shifted by half a tile, or by a third for tiles longer than 18 inches to reduce lippage. The count is the same as a straight grid, with waste of about 10 percent.
Diagonal
The tile grid is rotated 45 degrees. The number of full tiles is similar, but the perimeter is all cut triangles. Allow 15 percent.
Herringbone
Rectangular tiles are laid at right angles to each other. The pattern only works when the tile length is a whole multiple of its width. Allow 15 to 20 percent.
Mixed sizes
Modular patterns combine two or more sizes in a repeating unit. Manufacturers state the percentage of each size by area. Multiply your total area by each percentage and calculate each size separately.
Mosaic Sheets
Small mosaics come mounted on mesh sheets, usually close to 12 by 12 inches. Enter the sheet size as the tile size and set the grout joint to the gap between sheets, which is the same as the joint within the sheet. The result is the number of sheets.
Wall Tile and Showers
For a shower, measure each wall from the tub or pan up to the height you plan to tile. Add the areas together. Include the ceiling if it will be tiled, and any niche as five small rectangles: back, two sides, top and bottom. Wall layouts usually start from a level line one tile up from the lowest point, with the bottom row cut to fit last.
Substrate Preparation
Tile is rigid and will crack if the surface beneath it moves. On wood subfloors, add cement backer board or an uncoupling membrane. On concrete, fill cracks and check for flatness. In wet areas, use a waterproofing membrane behind or over the backer board. Standard drywall is not suitable behind shower tile.
Movement Joints
Large tiled areas need soft joints filled with flexible sealant where the tile meets walls and at intervals across the floor, typically every 20 to 25 feet indoors. These joints let the floor expand without tenting.