Quick answer
Area first, complete boxes last
Divide the rectangular surface area by one tile's face area. Apply the allowance selected for cuts, breakage, variation, and replacement stock. Round the required tile count upward, then divide by the exact carton quantity and round boxes upward.
Calculate my tile orderThe formula
Calculate tiles and boxes step by step
surface length × surface widthExact base tilessurface area ÷ one tile face areaRequired tilesround up (exact base tiles × (1 + waste ÷ 100))Complete boxesround up (required tiles ÷ tiles per box)Convert every dimension to one consistent unit before finding area. A 12 in × 24 in tile has a face area of 2 ft² because its dimensions are 1 ft × 2 ft.
Project input
Use an allowance that matches the layout
No percentage is correct for every installation. Straight runs in a simple rectangle may need less than diagonal or complex patterns with many cuts. Breakage, shade or lot variation, replacement stock, installer planning, and supplier return rules also affect the decision.
Reference: Daltile Tile & Natural Stone FAQs discusses planning for wastage and replacement stock. Treat any percentage as an editable assumption, not a guarantee.
Reference table
Tiles for 100 ft² with 10% allowance
These examples use nominal face dimensions and round only the final required tile count. Box quantity is not included because it varies by product.
| Tile size | Face area | Base tiles | With 10% |
|---|---|---|---|
| 12 × 12 in | 1 ft² | 100 | 110 |
| 12 × 24 in | 2 ft² | 50 | 55 |
| 18 × 18 in | 2.25 ft² | 44.45 | 49 |
| 24 × 24 in | 4 ft² | 25 | 28 |
Verify actual dimensions and the manufacturer's stated carton coverage. Nominal size can differ from the exact manufactured face size or package coverage used for ordering.
Worked example
A 12 ft × 10 ft floor with 12 × 24 in tiles
Use a 10% allowance and a carton containing eight tiles.
- Surface area: 12 × 10 = 120 ft².
- Tile face area: 1 × 2 = 2 ft².
- Exact base tiles: 120 ÷ 2 = 60.
- With 10% allowance: 60 × 1.10 = 66 required tiles.
- Complete boxes: round up (66 ÷ 8) = 9 boxes.
- Purchased quantity: 9 × 8 = 72 tiles.
The six tiles above the required 66 come from box rounding, not from increasing the chosen waste allowance. Reporting both values prevents those two sources of overage from being confused.
Layout check
Keep grout spacing separate from purchase area
TCNA guidance explains that joint choice depends on the tile, variation, edge, substrate, and installation. BuildMeasure uses the entered grout joint to compare row-and-column layouts, but it does not subtract joint area from the tile purchase quantity. Cut pieces may be reused, so a grid is not a cutting optimizer.
Sources: TCNA Grout FAQ and TCNA Ceramic Tile FAQ.
Before purchase
Verify what a rectangular formula cannot know
- Break irregular rooms into measured rectangles and combine the results.
- Confirm actual tile dimensions, package coverage, and tiles per box.
- Choose waste for the planned pattern, cuts, breakage, and repair stock.
- Confirm substrate, movement joints, mortar, grout, trim, and waterproofing separately.
- Follow current manufacturer instructions and qualified installer guidance.
Common questions
Tile quantity FAQ
How do I calculate how many tiles I need?
Divide the rectangular surface area by one tile's face area, multiply by one plus the project-specific waste percentage, round the required tiles upward, then divide by the tiles per box and round complete boxes upward.
Is 10% extra tile always enough?
No. Ten percent can be a planning starting point, but pattern, cuts, breakage, tile variation, installer method, replacement stock, and supplier rules can require a different allowance.
Does grout spacing reduce the tile purchase quantity?
BuildMeasure keeps grout spacing out of the area-based purchase formula. Joint width helps check rows and columns, while the explicit waste allowance handles cut loss without pretending every grid position consumes a new tile.
Can the formula estimate wall tile?
Yes for one rectangular wall. Enter width and height as the surface dimensions. Calculate separate rectangles and subtract measured openings carefully when the project is more complex.
Open the BuildMeasure Tile Calculator and enter the exact product carton quantity.