EngineeringFormulaCivil & Structural Engineering
Tile Calculator
Calculate how many tiles, boxes, and total cost you need to cover a rectangular room.
Planning a tile job? This calculator tells you exactly how many tiles to buy. Enter the room's length and width, the tile's length and width, and the grout gap between tiles - it counts tile columns and rows separately rather than dividing room area by tile area, so a room that isn't an exact multiple of the tile size is never under-counted. Add a waste factor for cuts and breakage, and a box size or per-tile price for a material cost estimate.
Room Dimensions
L · Direction tile columns run along
W · Direction tile rows run along
Tile Dimensions
tl · Individual tile's length
tw · Individual tile's width
g · Gap left between tiles for grout
Options
W% · 10% straight grid; 15%+ diagonal or complex patterns
tpb · Optional - leave blank to skip box count
$ · Optional - requires Tiles per Box
$ · Optional - used if box pricing isn't set
Solution
Enter room and tile dimensions to calculate your tile count.
N = ⌈Columns × Rows × (1 + W%)⌉
Formula Sheet
- NTotal Tiles
- LRoom Length
- WRoom Width
- tlTile Length
- twTile Width
- gGrout Gap
- W%Waste Factor
- tpbTiles per Box
Variables & Units
| Symbol | Variable | Description | Common Units |
|---|---|---|---|
| N | Total Tiles | Total number of tiles to purchase, rounded up and including the waste allowance. | |
| L | Room Length | The direction tile columns run along. | ft, m |
| W | Room Width | The direction tile rows run along. | ft, m |
| tl | Tile Length | The individual tile's length. | in, cm, mm |
| tw | Tile Width | The individual tile's width. | in, cm, mm |
| g | Grout Gap | The gap left between adjacent tiles for grout, in both directions. | in, mm |
| W% | Waste Factor | A decimal allowance for cuts and breakage beyond the row/column count (e.g. 0.10 = 10%). | |
| tpb | Tiles per Box | Number of tiles contained in one box, used to compute boxes needed. |
How to Use This Calculator
- 01Enter the room's length and width - tiles are assumed to run in a simple grid, columns along the length and rows along the width.
- 02Enter the tile's length and width, and the grout gap you're leaving between tiles.
- 03Set the Waste Factor (%) to account for cuts and breakage. A standard allowance is 10% for a straight grid layout; increase for diagonal or complex patterns.
- 04Optionally enter how many tiles come in one box and the price per box, or a price per individual tile, for a cost estimate.
- 05The calculator instantly shows tile columns, rows, total tiles, boxes needed, and cost. Buy full boxes from the same lot where possible so color, shade, and calibration match.
How the Formula Works
The calculator first finds how many tile columns are needed to span the room length, and how many rows to span the room width. N tiles laid side by side have only N − 1 grout joints between them, not N, so each count is ⌈(dimension + gap) / (tile size + gap)⌉ - adding one gap width to the room dimension before dividing - which correctly guarantees the tile grid covers the full room. Dividing the room dimension by tile pitch alone under-counts by one tile in some dimension-and-gap combinations.
Total tiles before waste is columns × rows. This row-by-column method is more accurate than the simpler room-area ÷ tile-area ratio many tile calculators use: a partial tile cut at the edge of a row still consumes a whole tile from stock, and the area-ratio method doesn't capture that - it can noticeably under-count on rooms that aren't an exact multiple of the tile size in both directions.
The waste factor adds a percentage buffer on top of the row/column count before a final round-up, covering cuts, mis-cuts, and breakage beyond what the grid layout itself requires.
Boxes needed is the total tile count divided by tiles per box, rounded up. Cost is calculated from box pricing when both tiles-per-box and price-per-box are supplied (the realistic case for boxed tile, since you pay for whole boxes); otherwise it falls back to price-per-tile if supplied.
Worked Example 01
Standard bathroom floor
Known
- Room Length (L): 10 ft
- Room Width (W): 12 ft
- Tile Length (tl): 12 in
- Tile Width (tw): 12 in
- Grout Gap (g): 1/8 in
- Waste Factor (W%): 10%
Formula
Columns = ⌈(L + g) / (tl + g)⌉
Substitution
Columns = ⌈(120+0.125)in / 12.125in⌉ = 10, Rows = ⌈(144+0.125)in / 12.125in⌉ = 12, N = ⌈10 × 12 × 1.10⌉
Result
132 tiles
A 10 by 12 foot bathroom using 12-inch tiles with a 1/8-inch grout gap needs 10 columns and 12 rows - 120 base tiles. Adding a 10% waste buffer gives 132 tiles to order.
Worked Example 02
Metric kitchen floor, where the grid method matters
Known
- Room Length (L): 4 m
- Room Width (W): 3 m
- Tile Length (tl): 30 cm
- Tile Width (tw): 30 cm
- Grout Gap (g): 3 mm
- Waste Factor (W%): 10%
Formula
Columns = ⌈(L + g) / (tl + g)⌉
Substitution
Columns = ⌈4.003/0.303⌉ = 14, Rows = ⌈3.003/0.303⌉ = 10, N = ⌈14 × 10 × 1.10⌉
Result
154 tiles
A 4 m by 3 m kitchen using 30 cm tiles needs 14 columns and 10 rows - 140 base tiles, plus 10% waste for 154 total. A simple room-area ÷ tile-area estimate would suggest only 147 tiles here, 7 short of what the grid actually requires, because neither room dimension is an exact multiple of the tile pitch.
Applications
- 01Estimating tile quantity and material cost for a bathroom, kitchen, or floor tiling project
- 02Quick quantity takeoff for contractor bidding or homeowner budgeting
- 03Comparing tile quantity and cost between different tile sizes before ordering
- 04Checking whether a different tile size reduces edge cuts before buying boxes
Assumptions
- 01The room is a single straight rectangle, tiled in a simple grid - tile columns run the full room length direction, rows run the full width direction.
- 02All tiles are the same size throughout the room, laid with a consistent grout gap in both directions.
- 03Waste factor is applied on top of the row/column count, not folded into it - the row/column count already reflects the minimum whole tiles needed to physically cover the room.
Where This Model Stops
- 01Does not model L-shaped rooms, alcoves, islands, or other openings - an irregular room should be broken into rectangular sections and calculated separately, then summed.
- 02Does not calculate grout or thinset/adhesive quantities. Grout coverage depends on tile size, joint width and depth, and the specific grout product's density - use the manufacturer's own coverage chart or calculator for that product. Thinset coverage depends on trowel notch size and substrate, and is also best sourced from the adhesive manufacturer's spec sheet.
- 03Does not account for diagonal, herringbone, or other non-grid layouts beyond the waste-factor adjustment - those patterns have real, layout-specific cutting geometry this calculator doesn't model directly; increase the waste factor per the guidance above as a practical substitute.
- 04Does not account for tile shade variation, dye-lot availability, or attic/basement spare tile storage for future repairs.
References
- [1]
Tile Calculator: Estimate Tiles Needed
Inch Calculator
Industry reference for room-area and waste-factor conventions used in residential tile estimating, including layout-dependent waste guidance (straight, diagonal, complex patterns).
- [2]
Tile Calculator
Omni Calculator
Reference for the tile-count, box-conversion, and cost-estimate structure used by tiling-focused calculators, including the room-dimension and grout-gap input model.
Frequently Asked Questions
What waste factor should I use?
10% is standard for a simple grid layout with cuts mostly at the room's edges. Use 15% for a diagonal layout, since every edge tile needs a 45-degree cut, and 20% or more for herringbone, mosaic borders, or a room with many obstacles and jogs.
Why does this calculator count rows and columns instead of just dividing room area by tile area?
Because a partial tile cut at the edge of a row still uses up a whole tile from stock, and a simple area ratio doesn't capture that. Counting columns and rows separately, each rounded up independently, gives the actual number of whole tiles the grid requires - the second worked example above shows a real 7-tile gap between the two methods on the same room.
Does this calculate how much grout or thinset I need?
No - grout coverage depends on tile size, joint width and depth, and the specific grout product's density, and thinset coverage depends on trowel notch size and substrate. Both are best estimated from the manufacturer's own coverage chart for the exact product you're using, rather than a generic formula.
Should I use box pricing or per-tile pricing?
Use box pricing (Tiles per Box and Price per Box) whenever your tile is sold by the box, since that reflects what you actually pay - a partial box still costs a full box. Use Price per Tile only if you're buying loose, individually priced tiles.
Should I buy extra tiles beyond the calculator's waste factor?
For exact color and size matching, many installers keep at least one unopened box from the same lot for future repairs, especially for discontinued or specialty tile. That spare box is separate from the waste used during installation.