Tile Calculator
Work out how many tiles and boxes a floor, wall or backsplash needs, with the grout joint, a waste allowance for your layout and a grout estimate.
Grout depth and cost (optional)
Covers 120 ft² with 10% extra for cuts and breakage.
Room 12 × 10 ft, 1/8 in grout joint, straight layout.
Boxes to buy
130 tiles in total, exactly the number needed. Buy boxes with the same lot and shade number.
Your calculation
The same steps the calculator runs, with your numbers.
- Area: 12 × 10 = 120 ft².
- One tile with its joint: (12 + 0.125) × (12 + 0.125) = 147.02 in².
- Tiles: 120 × 144 ÷ 147.02 = 117.54.
- Add 10% waste: 117.54 × 1.1 = 129.29, rounded up to 130 tiles.
- Boxes: 130 ÷ 10 = 13 boxes.
- Grout: (12 + 12) ÷ (12 × 12) × 0.125 × 0.375 × 144 × 120 = 135 in³, × 25 ÷ 390 = 8.7 lb.
Other tile sizes for this area
Same area, grout joint, thickness and waste allowance, with only the tile size changed.
| Tile size | Tiles to buy | Grout (lb) |
|---|---|---|
| 6 × 6 in | 507 | 17.3 |
| 12 × 24 in | 65 | 6.5 |
| 18 × 18 in | 58 | 5.8 |
| 24 × 24 in | 33 | 4.3 |
| 24 × 48 in | 17 | 3.2 |
An estimate from the dimensions you enter. Lay out the room before cutting, and check the joint width and coverage figures from your tile and grout manufacturers.
How the Tile Calculator Works
This tile calculator divides the area you want to cover by the area of one tile plus its grout joint, adds a waste allowance for cuts and breakage, and rounds up to whole tiles and whole boxes. It works the same way for floor tile, wall tile, shower walls and kitchen backsplashes, because each is a flat area covered by a grid of tiles.
The grout joint matters more than it looks. Each tile occupies its own size plus one joint width in each direction, so a 12 inch tile with a 1/8 inch joint takes up a 12.125 inch square. Leaving the joint out makes the count slightly high, which is safe but wasteful on large floors.
Areas in square feet are multiplied by 144 because one square foot holds 12 × 12 = 144 square inches. In metric mode the room is in square meters and the tile in millimeters, so the area is multiplied by 1,000,000 square millimeters per square meter instead.
Tiles per Square Foot Chart
How many tiles of common sizes cover 100 square feet, with a 1/8 inch grout joint. The last column adds a 10 percent waste allowance and rounds up to whole tiles.
| Tile size | Tile area | Tiles per ft² (no joint) | Tiles per 100 ft² | With 10% waste |
|---|---|---|---|---|
| 3 × 6 in | 0.125 ft² | 8.000 | 752.3 | 828 |
| 4 × 4 in | 0.111 ft² | 9.000 | 846.3 | 931 |
| 6 × 6 in | 0.250 ft² | 4.000 | 383.8 | 423 |
| 6 × 24 in | 1.000 ft² | 1.000 | 97.5 | 108 |
| 12 × 12 in | 1.000 ft² | 1.000 | 97.9 | 108 |
| 12 × 24 in | 2.000 ft² | 0.500 | 49.2 | 55 |
| 18 × 18 in | 2.250 ft² | 0.444 | 43.8 | 49 |
| 24 × 24 in | 4.000 ft² | 0.250 | 24.7 | 28 |
| 24 × 48 in | 8.000 ft² | 0.125 | 12.4 | 14 |
A 6 × 24 inch plank and a 12 × 12 inch square have the same face area, yet the plank needs slightly more tiles because it has more joint length per tile. Narrow tiles always lose a little more coverage to grout than square tiles of the same area.
How Much Extra Tile to Buy
BuildDirect's tile and stone installation guide advises ordering 10 to 15 percent more tile than the measured area to allow for cuts and breakage, and notes that diagonal, herringbone and other patterned layouts may require more. Choosing a layout in the calculator sets the waste allowance to these defaults, which you can change:
| Layout | Calculator default | Why it wastes tile |
|---|---|---|
| Straight (grid) | 10% | Cuts only at the walls; an offcut from one end often fits the other |
| Brick or offset | 10% | Alternate rows start with a part tile |
| Diagonal | 15% | Every edge tile is cut at an angle |
| Herringbone | 15% | Angled cuts at every wall, few reusable offcuts |
Raise the allowance for a small room, an L shaped floor, many pipes or corners, or large format tile, where each miscut wastes more material. Tile is made in batches, so the same guide says to check that every box carries the same shade or lot number and to keep leftover tiles for future repairs.
Grout Joint Size and How Much Grout You Need
The Ceramic Tile Foundation quotes ANSI A108.02, Section 4.3.8: the actual grout joint must be at least three times the actual variation in the facial dimensions of the tile supplied, and in no case less than 1/16 inch. A tile batch that varies by 1/16 inch needs a 3/16 inch joint. For brick or running bond patterns with any side longer than 15 inches, Section 4.3.8.1 calls for an average joint of at least 1/8 inch for rectified tile and 3/16 inch for calibrated tile.
BuildDirect's guide recommends sanded grout for joints 1/8 inch and wider and unsanded grout for narrower joints, and unsanded grout on marble and glass, which sanded grout can scratch. The grout tile in the results applies the width rule. Some fine aggregate grouts work across the range: Laticrete rates its sand free PERMACOLOR for joints from 1/16 to 1/2 inch.
The figure of 390 cubic inches per 25 lb bag comes from Custom Building Products' coverage chart for Polyblend HP. The chart lists 348 square feet per bag for 12 × 12 × 3/8 inch tile with a 1/8 inch joint, and 348 × 1.125 = 391.5 cubic inches. Its rows for tiles 6 inches and larger give 387 to 399 cubic inches, while mosaic rows give more, so the estimate runs high for mosaics. Products differ: Laticrete lists 536 square feet per 25 lb bag of PERMACOLOR for 12 × 24 × 3/8 inch tile at 1/8 inch, against 461 square feet in the Custom chart, so this estimate leans toward buying slightly more.
| Tile size and thickness | Grout per 100 ft², 1/8 in joint | Grout per 100 ft², 1/4 in joint |
|---|---|---|
| 3 × 6 × 5/16 in | 18.0 lb | 36.1 lb |
| 6 × 6 × 1/4 in | 9.6 lb | 19.2 lb |
| 12 × 12 × 3/8 in | 7.2 lb | 14.4 lb |
| 12 × 24 × 3/8 in | 5.4 lb | 10.8 lb |
| 24 × 24 × 3/8 in | 3.6 lb | 7.2 lb |
Doubling the joint width doubles the grout, and smaller tiles need more grout because they have more joint per square foot.
How to Measure for Tile
- Floors. Measure the length and width at the widest points. Split an L shaped room into rectangles and add the areas.
- Subtract fixed items. A tub, kitchen island or built in cabinets that will not be tiled under.
- Walls. Multiply the wall width by the tiled height, then subtract windows and doors.
- Tile size. Measure an actual tile. Nominal sizes on the box can differ from the real face size.
- Box count. Read the pieces per box from the carton.
Common Mistakes
- Dividing square feet by square inches. Convert one first: 120 ft² is 17,280 in².
- Skipping the waste allowance. 118 tiles covers the 12 × 10 ft example with nothing to spare; 130 allows for cuts.
- Rounding boxes down. 12.8 boxes means buying 13.
- Mixing lots. Shades can differ between batches.
- Ignoring narrow tiles. Planks and mosaics need more grout.
Wall, Backsplash and Metric Examples
Kitchen backsplash
Backsplashes often come out with many spare tiles, because small tiles are packed in large boxes. Here the fourth box leaves 64 tiles spare, which is useful for later repairs.
Metric floor
NIST defines one square foot as exactly 0.09290304 square meters and one inch as 25.4 millimeters, the factors the calculator uses when you switch units. The metric grout figure uses the same 390 cubic inches per 25 lb bag, which works out to 1.774 kilograms per liter of joint.
Frequently Asked Questions
How many tiles do I need for a 10x12 room?
A 10 by 12 foot room is 120 square feet. With 12 by 12 inch tiles and a 1/8 inch grout joint, each tile plus its joint covers 12.125 × 12.125 = 147.02 square inches, or 1.021 square feet. Divide 120 × 144 = 17,280 square inches by 147.02 to get 117.54 tiles, which is 118 tiles with no allowance. Adding 10 percent for cuts and breakage gives 129.29, so buy 130 tiles. At 10 tiles per box that is 13 boxes.
How do I calculate how many tiles I need?
Multiply the room's length by its width to get the area, then subtract fixed areas such as a tub or cabinets. Add the grout joint to each tile dimension and multiply to get the area one tile covers. Divide the floor area by the tile area in the same units, multiply by 1 plus your waste allowance, and round up to a whole tile. Finally, divide by the number of tiles per box and round up again, because tile is sold in whole boxes.
How many 12x24 tiles do I need for 100 square feet?
With a 1/8 inch grout joint, a 12 by 24 inch tile covers 12.125 × 24.125 = 292.52 square inches, or 2.031 square feet. 100 square feet is 14,400 square inches, and 14,400 ÷ 292.52 = 49.23 tiles before waste. Adding 10 percent gives 54.15, so buy 55 tiles. If the tile is sold 8 to a box, that is 7 boxes with 1 tile spare. For a brick pattern with tiles longer than 15 inches, ANSI A108.02 calls for an average joint of at least 1/8 inch for rectified tile and 3/16 inch for calibrated tile.
How much extra tile should I buy?
BuildDirect's tile installation guide advises ordering 10 to 15 percent more tile than the measured area to allow for cuts and breakage, and notes that diagonal, herringbone and other patterned layouts may need more. This calculator uses 10 percent for straight and offset layouts and 15 percent for diagonal and herringbone, and you can change the figure. Raise it for small rooms, many corners or large format tile. Keep the leftover tiles, along with the box labels showing the lot and shade, for future repairs.
How much grout do I need?
Grout fills the joints, so the amount depends on tile size, joint width and joint depth, which is usually the tile thickness. The volume per square foot is (L + W) ÷ (L × W) × joint width × depth × 144 cubic inches, with sizes in inches. For 12 by 12 inch tile, 3/8 inch thick, with a 1/8 inch joint, that is 1.125 cubic inches per square foot, or 135 cubic inches for 120 square feet. Custom Building Products' coverage chart works out to about 390 cubic inches per 25 lb bag, so this floor needs about 8.7 lb, or one bag.
What size grout joint should I use for tile?
ANSI A108.02, as quoted by the Ceramic Tile Foundation, says the grout joint must be at least three times the actual variation in the tile's facial dimensions and never less than 1/16 inch. Tile that varies by 1/16 inch therefore needs a 3/16 inch joint. For brick or running bond patterns with any side longer than 15 inches, the average joint must be at least 1/8 inch for rectified tile and 3/16 inch for calibrated tile. The tile manufacturer's recommended joint is the best starting point.
Sources & References
- Ceramic Tile Foundation. ANSI Standards: A Tile Installer's Best Friend! (quotes ANSI A108.02 Sections 4.3.8 and 4.3.8.1 on minimum grout joints). ceramictilefoundation.org
- BuildDirect. Installation Instructions: Tile and Stone (order 10 to 15 percent extra, patterned layouts may need more, matching lots, sanded grout for joints 1/8 inch and wider). builddirect.com
- Custom Building Products. Polyblend HP grout, square foot coverage per 25 lb bag. custombuildingproducts.com
- LATICRETE. PERMACOLOR Grout sell sheet (coverage per 25 lb bag). laticrete.com
- NIST. Guide to the SI, Appendix B.8: Factors for Units Listed Alphabetically (square foot to square meter, inch to millimeter). nist.gov
Results are estimates based on the dimensions entered and the coverage figures above. Every number on this page was recomputed with the same formulas the calculator uses. Methodology reviewed: 2026.