Measure the tile area
For a rectangular floor or wall, multiply length by width to determine the total area in square feet.
Calculate the area of one tile
When tile dimensions are given in inches, multiply tile length by tile width to find square inches, then divide by 144 to convert to square feet.
Calculate the basic tile quantity
Example with 12 × 12 inch tiles
A 12 × 12 inch tile covers approximately one square foot. A 120-square-foot rectangular room therefore requires about 120 tiles before allowing for cuts or breakage.
How much extra tile should you allow?
Waste depends on the room shape, tile pattern, tile size and installer layout. Straight layouts in simple rooms generally create less waste than diagonal layouts or detailed patterns.
- Include additional material for cut tiles.
- Allow for occasional breakage or defects.
- Complex patterns can increase offcuts.
- Matching spare tiles can be useful for future repairs.
Tile boxes and package coverage
Many tiles are purchased by the box rather than individually. Once the adjusted square footage is known, divide it by the square-foot coverage per box and round up.
Tile sizes are often nominal, and grout-joint layouts can affect real coverage slightly. For purchasing, use the coverage specified on the product packaging.
Worked example: estimating tiles for a floor
Suppose a rectangular floor is 12 feet long and 10 feet wide. Its area is 120 square feet. If each tile covers 1 square foot, the theoretical requirement is 120 tiles before waste. Adding a 10 percent allowance increases the planning quantity to 132 tiles. If the tiles are sold by the box, divide the required tile quantity or area by the coverage stated on the box and round up to a whole package.
Why tile layout changes the waste allowance
A simple rectangular room with a straight tile layout may require fewer cuts than a room with several corners, columns, doorways or diagonal patterns. Large-format tiles can also create more unusable offcuts when the remaining piece cannot be used elsewhere. The waste allowance is therefore a planning margin rather than a universal percentage.
Measure separate areas before adding them together
For irregular floors or walls, divide the surface into rectangles or other simple sections. Calculate the area of each section separately, then add them together. Openings that will not receive tile can be deducted when they are large enough to materially affect the estimate, while very small deductions are sometimes left in the total as part of the waste allowance.
Common tile-estimating mistakes
- Using tile dimensions without converting them to the same unit as the room dimensions.
- Ordering exactly the theoretical quantity with no allowance for cuts or breakage.
- Forgetting that tiles may be sold by box coverage rather than individually.
- Using nominal tile size when the manufacturer's stated coverage or actual size is different.
- Failing to account for a layout that creates many edge or diagonal cuts.