Tile Calculator
Enter the area and the tile size to get how many tiles to buy, with waste for your layout. The same result estimates the thinset bags for your trowel notch and the sanded grout for your joint width.
Quick answer: 100 ft² of 12 × 12 in tile with 1/8 in joints is 97.95 tiles, or 108 with 10% waste, plus 2 bags of 50 lb thinset and about 7.9 lb of sanded grout.
Tile count is the area divided by the area of one tile plus one grout joint, then increased by a waste percentage for cuts and breakage and rounded up. Thinset comes from the coverage per 50 lb bag for your trowel, and grout is estimated from the joint volume.
Example: 100 ft² of 12 × 12 in tile with 1/8 in joints is 97.95 tiles. With 10% waste that is 108 tiles. Thinset on a 1/4 in square trowel is 2 bags of 50 lb, and sanded grout is about 7.9 lb, which is one 25 lb bag.
Method
How this calculator works
The tile count is plain geometry. Waste is a convention you can change, and thinset and grout are estimates from manufacturer data. Your carton and bag labels should replace them when they differ.
Area of one tile and its joint
Each tile carries one grout joint along two of its edges, so the calculator measures it as (width + joint) × (length + joint). Dividing the area by that gives the count before waste. Sizes and joints are in inches.
Area per tile (ft²) = (W + J) × (L + J) ÷ 144Net tiles = Area (ft²) ÷ Area per tileWaste by layout
Cuts, breakage and mistakes mean you buy more than the net count. The presets are 10% for a straight grid, 15% for diagonal and 20% for herringbone or mosaic. They are industry rules of thumb, not a standard. Flooring retailers publish similar ranges (7 to 10% straight, about 15% diagonal, 15 to 20% herringbone). Type a number in Waste override to replace the preset.
Tiles to buy = ceil(Net tiles × (1 + Waste ÷ 100))Boxes = ceil(Tiles to buy ÷ Tiles per box)Thinset bags by trowel
Coverage per 50 lb bag comes from the CUSTOM Building Products VersaBond chart, and the calculator uses the minimum of each range to stay on the safe side. The area is the area to tile, without the tile waste. Other brands differ, so enter the figure on your bag. Tile of 15 in or more needs a deeper notch and back-buttering, which uses more thinset than the chart row. The same data sheet asks for at least 80% mortar contact in dry areas and 95% in wet areas.
Thinset bags = ceil(Area ÷ Coverage per bag)Grout weight and bags
Grout is the volume of the joints times a density. Each tile owns half of its four joints, so the joint length per tile is its width plus its length. The density, 0.064 lb per cubic inch of sanded cementitious grout, was calibrated against a manufacturer coverage chart: within about -2% to +1% of it for 12 × 12 and 18 × 18 in tile, and generous (more grout than the chart) for small tile and mosaics. It is not verified for epoxy or unsanded grout, so use the bag's coverage there. 10% is added for waste.
Grout (lb) = Area × 144 × (W + L) ÷ (W × L) × Thickness × Joint × 0.064 × 1.10Grout bags = ceil(Grout (lb) ÷ Bag size (lb))Thinset coverage by trowel notch (the chart behind step 3)
| Trowel notch | Minimum, ft² per 50 lb bag (used) | Maximum, ft² per 50 lb bag |
|---|---|---|
| 1/4 × 1/4 × 1/4 in square | 90 | 100 |
| 1/4 × 3/8 × 1/4 in square | 60 | 67 |
| 1/2 × 1/2 × 1/2 in square | 42 | 47 |
| 3/4 × 9/16 × 3/8 in U-notch, 45° | 34 | 38 |
| 3/4 × 9/16 × 3/8 in U-notch, 30° | 42 | 47 |
What each field does
| Field | What to enter |
|---|---|
| Area to tile | Pick Length × width for a rectangular room, or Total area if you already know it. For a wall, enter the wall area after you subtract windows, niches and anything else you will not tile. The calculator has no cutout fields. |
| Tile size | The nominal size printed on the box, width × length. Choose Custom for rectified or metric tile whose real size differs from the nominal one. |
| Custom width and Custom length | Used only when Tile size is set to Custom. With any listed size they are ignored. Enter inches in the US view or centimeters in the metric view. |
| Grout joint width | Inches in the US view (1/8 in is 0.125, and fractions such as 3/16 work) or millimeters in the metric view. A joint of 0 is allowed for tight rectified tile, but then no grout is counted. |
| Tile thickness | Used for the grout estimate only. It does not change the tile count. Floor tile is often 3/8 in thick. |
| Layout and Waste override | Layout sets 10%, 15% or 20% waste. If you type a percentage in Waste override, that number replaces the layout preset. |
| Tiles per box | Optional. Enter the count printed on the carton to see how many boxes to buy. |
| Trowel notch and Thinset coverage | The notch picks a coverage row from the thinset chart. If your bag states its own coverage per 50 lb bag, enter it in Thinset coverage to replace the chart. |
| Grout bag size and Grout coverage | Bag size sets how many bags the grout weight rounds up to. If your grout label gives coverage per bag, enter it in Grout coverage to replace the formula. |
Worked example: a 100 ft² floor in 12 × 12 in tile, 1/8 in joints
Arithmetic checkedStraight grid with the 10% waste preset, 3/8 in thick tile, 10 tiles per box, a 1/4 in square trowel and a 25 lb bag of sanded grout. The tile count is the calculator’s own example result. The chart check agrees: the maker’s chart gives 348 ft² per 25 lb bag for this tile and joint, and 100 ÷ 348 of a bag is 7.2 lb.
| Step | Math | Result |
|---|---|---|
| Area to tile | entered | 100 ft² |
| One tile plus its joint | (12 + 0.125) × (12 + 0.125) ÷ 144 | 1.0209 ft² |
| Tiles without waste | 100 ÷ 1.0209 | 97.95 tiles |
| Add 10% waste | 97.95 × 1.10 | 107.74 tiles |
| Round up | ceil(107.74) | 108 tiles |
| Boxes, if 10 tiles per box | 108 ÷ 10, rounded up | 11 boxes |
| Thinset, 1/4 in square trowel | 100 ÷ 90, rounded up | 2 bags of 50 lb |
| Grout, before waste | 100 × 144 × (24 ÷ 144) × 0.375 × 0.125 × 0.064 | 7.20 lb |
| Grout with 10% waste | 7.20 × 1.10 | 7.92 lb |
| Grout bags | 7.92 ÷ 25, rounded up | 1 bag of 25 lb |
| You would buy | 108 tiles, 2 bags of thinset, 1 bag of grout | |
Disclaimer
Results are planning estimates based on the dimensions and assumptions you enter. They are not engineering, structural or building-code advice. Product yields, densities and coverage vary by manufacturer, batch and site conditions. Check product labels, your supplier and your local building department before you order materials or start work. Read the full calculation disclaimer.
Accuracy
What affects your estimate
The count is close to exact. Waste, thinset and grout depend on the layout, the products and the installer.
Layout decides the waste
A straight grid wastes the least. Diagonal and herringbone cut more tile at every edge, so 15% or 20% is a better start. Rooms with many corners, tubs or cabinets add more. For the same 100 ft² floor, 20% gives 118 tiles instead of 108.
The joint changes grout more than tiles
Going from a 1/8 in to a 3/16 in joint on 12 × 12 tile moves the count from 108 to 107, but the grout estimate from 7.9 lb to 11.9 lb. A wide joint is mostly a grout decision.
Nominal size is not always real size
Rectified and metric tile often differ a little from the nominal size on the box. Choose Custom and enter the measured size, and use the joint your layout calls for.
Thinset and grout vary by product
Coverage depends on the brand, trowel, back-buttering and how flat the surface is. The numbers here are estimates from one thinset chart and one grout chart. Your bag's coverage is the one to trust.
Substrate preparation, flatness, waterproofing and movement joints follow TCNA guidance, the tile and mortar makers' instructions and local code. They are not calculated here. Buy all the tile from one lot and keep a few spare for repairs.
Common mistakes
Entering the room area without the cutouts
The calculator tiles every square foot you give it. Subtract tubs, cabinets and anything you will not tile before you enter the area, and for walls do the same for niches and windows.
Using the straight-grid waste on a diagonal or herringbone floor
More cuts need more tile. If you pick the layout, the percentage follows. If you override it, set it yourself.
Treating thinset and grout as exact
They are planning estimates. Read the coverage on your bag, and enter it in the thinset or grout coverage field so the calculator uses your number.
Ordering the tile count instead of whole boxes
Tile is sold in cartons. 108 tiles at 10 per box is 11 boxes, which is 110 tiles. Enter the tiles per box, buy the whole boxes, and keep the extras as spares.
Questions people ask
How do I calculate how many tiles I need?
Divide the area to tile by the area of one tile plus its joint, add the waste for your layout and round up. For 100 ft² of 12 × 12 in tile with 1/8 in joints that is 97.95 tiles, and 108 with 10% waste. The guide on how many tiles you need walks through it room by room.
How much extra tile should I buy?
The presets are 10% for a straight grid, 15% for diagonal and 20% for herringbone or mosaic. These are conventions, not a standard. Add more for a room with many cuts, and keep a few extra tiles from the same lot for repairs.
How many 12×24 tiles do I need for a 10 ft × 12 ft room?
The area is 120 ft². One 12 × 24 in tile with a 1/8 in joint takes (12.125 × 24.125) ÷ 144 = 2.0314 ft², so the net count is 59.07. With 10% waste that is 65 tiles, and 68 tiles with the 15% diagonal preset.
How do I use the calculator for a shower wall or a backsplash?
Use Total area and enter the wall area after you subtract windows, niches and fixtures. For example, 60 ft² of 3 × 6 in tile with 1/8 in joints is 451.4 tiles net and 497 with 10% waste. Set the tile thickness for the grout estimate, often about 1/4 in for wall tile. Check the maker's instructions for waterproofing behind the tile.
How many boxes of tile do I need?
Enter the number of tiles per box from the carton. The calculator divides the tiles to buy by that number and rounds up: 108 tiles at 10 per box is 11 boxes. If the carton lists square feet instead, divide the area with waste by that figure and round up.
How do I enter a tile size that is not in the list?
Set Tile size to Custom and fill in Custom width and Custom length. Those two fields are used only when Custom is selected. They take inches in the US view and centimeters in the metric view.
How much thinset and grout do I need?
Thinset is the area divided by the coverage per 50 lb bag for your trowel, rounded up, so 100 ft² on a 1/4 in square trowel (90 ft² per bag) is 2 bags. Grout is the joint volume times a density, so 100 ft² of 12 × 12 in tile with a 1/8 in joint is about 7.9 lb with waste. Both are estimates, and a bag label overrides them.
Related calculators and guides
Sources
Where the numbers come from
- CUSTOM Building Products VersaBond Professional Tile Mortar (TDS-119): coverage chart by trowel and mortar contact levels (one product; other brands differ), accessed October 16, 2026.
- CUSTOM Building Products Polyblend Plus Sanded Grout (TDS-129): joint range and bag sizes, accessed October 16, 2026.
- CUSTOM Polyblend Plus coverage chart grout coverage per 25 lb bag, used to calibrate the grout density (a derived estimate), accessed October 16, 2026.
- Lumber Liquidators flooring waste ranges by layout (retailer guidance for flooring, not a tile standard), accessed October 16, 2026.