How Many Tiles Do I Need? Figure Out Square Footage, Grout Joints, Waste and Boxes

100 sq ft of 12 in × 12 in tile with a 1/8 in joint takes 97.9 tiles before waste and 108 tiles with a 10% waste allowance.

To size your own floor, measure it in square feet (length × width), divide by the area of one tile plus its grout joint, add about 10% for waste (15% for a diagonal layout) and round up. If you buy by the box, divide the area with waste by the square feet one box covers, and round up to whole boxes.

How do you figure out the square footage for tile?

1. Measure the length and width of the space in feet. Use feet and decimals: 12 ft 6 in is 12.5 ft.
2. Multiply length by width. A 12 ft × 15 ft room is 180 sq ft.
3. For an L-shape or a room with an alcove, split it into rectangles, find the area of each and add them. The how to calculate square feet guide and the square footage calculator cover more shapes.
4. Subtract areas that will not be tiled, such as a tub or a built-in vanity, only if the tile stops at them. If the tile runs under a toilet or a vanity, keep the area in.
5. For a wall or backsplash, area is length × height.

The tile count formula

area of one tile + joint (sq ft) = (tile length in + joint in) × (tile width in + joint in) ÷ 144
tiles before waste = floor area (sq ft) ÷ area of one tile + joint
tiles to buy = ceil( tiles before waste × (1 + waste) )

The 144 is the number of square inches in a square foot. Each tile owns its own face plus one grout joint on each of two sides, so its footprint is (length + joint) × (width + joint). Use the actual size printed on the box, which can differ a little from the nominal size. Multiply the waste in (1.10), do not add 10 to the count.

Tiles per 100 sq ft by size

The joint matters most on small tiles. A 1/8 in joint takes 6% off the count for 4 in × 4 in tile and only 2% off for 12 in × 12 in tile.

To use the table for another floor, scale it: for 250 sq ft of 12 × 12 in tile, 250 ÷ 100 × 97.9 = 244.9 tiles before waste. Work the buy column from the unrounded figure, not from a count you already rounded up.

Worked example: a 5 × 8 ft bathroom floor

The floor is 12 in × 12 in tile with a 1/8 in joint, laid straight, with 10% waste.

• Area: 5 × 8 = 40 sq ft.
• Tile plus joint: 12.125 × 12.125 ÷ 144 = 1.0209 sq ft.
• Tiles before waste: 40 ÷ 1.0209 = 39.18.
• With 10% waste: 39.18 × 1.10 = 43.10, so 44 tiles.

With 12 in × 24 in tiles the same floor takes 40 ÷ (12.125 × 24.125 ÷ 144) = 19.69 tiles before waste and 21.66 with 10%, so 22 tiles. A bigger tile has fewer cuts per square foot but more waste per cut, which is why some layouts call for 15% to 20%.

How many boxes of tile do I need?

boxes = ceil( floor area × (1 + waste) ÷ square feet per box )

The square feet per box is printed on the carton. It is a product figure, not a rule, and it varies widely: check your box rather than relying on an average. It is normally the face area of the tiles inside, so buying by box area leaves out the grout joint. That makes the box method slightly generous, by about 2% for 12 in × 12 in tile with a 1/8 in joint.

Take a 12 ft × 15 ft room of 180 sq ft, and suppose each box covers 20 sq ft. That figure is only an illustration.

• With 10% waste: 180 × 1.10 = 198 sq ft.
• Boxes: 198 ÷ 20 = 9.9, so 10 boxes, which leaves 200 − 180 = 20 sq ft over.
• On a diagonal layout with 15% waste: 180 × 1.15 = 207 sq ft, and 207 ÷ 20 = 10.35, so 11 boxes.

Always round up to whole boxes. Flooring guides from retailers often suggest buying one or two extra cartons for later repairs. For laminate, vinyl plank or hardwood sold by the box, the Flooring Calculator does the same box count with waste by layout.

How much waste should you add?

No standards body sets a waste allowance for tile. The values below are installer and retailer rules of thumb, so treat them as starting points and adjust for your room.

The plank-flooring rows come from retailer and manufacturer guides for hardwood and similar flooring, and are included so you can compare. If the product label gives a waste cap, the label wins.

Thinset and grout

Both are estimates that depend on the product. CUSTOM Building Products’ VersaBond chart lists 90 to 100 sq ft per 50 lb bag with a 1/4 in square-notch trowel, 60 to 67 sq ft with a 1/4 × 3/8 in trowel and 42 to 47 sq ft with a 1/2 in square-notch trowel. Using the low end is the safe choice, since large tile and back-buttering use more. For 100 sq ft with the 1/4 in trowel, 100 ÷ 90 = 1.11, so 2 bags. Other brands differ, so use the coverage on your bag.

Grout depends on tile size, tile thickness and joint width. The industry formula for joint volume, calibrated against CUSTOM’s Polyblend Plus sanded grout chart, is: pounds = area × 144 × ((L + W) ÷ (L × W)) × thickness × joint × 0.064, with L, W, thickness and joint in inches. For 100 sq ft of 12 × 12 in tile, 3/8 in thick, with a 1/8 in joint: 100 × 144 × (24 ÷ 144) × 0.375 × 0.125 × 0.064 = 7.2 lb. Adding 10% gives 7.9 lb, within one 25 lb bag. That matches the chart, which has 348 sq ft per 25 lb bag for these sizes. The 0.064 figure is for sanded cementitious grout only. Epoxy and unsanded grout can differ, so use the bag’s own chart for those.

Assumptions and limits

• One tile size and a uniform joint. Mixed sizes and patterns need each part counted on its own.
• The floor is flat and rectangular, or split into rectangles. Curved walls and angles add cuts.
• This guide counts materials. Subfloor flatness, deflection, waterproofing and movement joints follow the tile industry standards and the maker’s instructions, and are not covered here. Ask the tile or thinset maker or a licensed contractor.
• Large-format tile (about 15 in and up) generally needs a larger trowel. Check the thinset label before you buy.

Common questions