Flooring and Tile Calculator

What this calculator answers

How many boxes of flooring or tile to buy for one or more rooms. It adds up rectangles, takes out islands, hearths and tubs, adds a waste allowance for your layout and rounds up to whole boxes last. It also shows how much of what you buy is left over, how many tiles you will lay when the grout joints are counted, and what the boxes cost per box, per square foot and per square foot of your floor.

How to use it

• Units: US (feet and inches) or metric (meters, centimeters, millimeters). Switching converts what you have typed.
• Material: Flooring for planks or sheets sold by the area per box (laminate, vinyl, engineered or solid wood). Tile counts tiles one by one with their grout joints.
• Measure by: Room sizes for a list of rectangles, or Total area if you already know the square footage.
• Areas: one rectangle per row. Feet and inches can be typed as 15' 6", 15 ft 6 in, 15-6 or 15.5. Tick Cut-out for anything the floor won’t cover, such as a kitchen island, a hearth or a built-in tub, and put that row right below the area it sits in. Paste rows takes name, length, width and cut-out columns copied from a spreadsheet.
• Tile length, tile width and grout joint (tile only): the tile size from the carton and the gap between tiles. The joint accepts fractions such as 1/8 or 3/16; type 0 for none.
• Box contents (tile only): the number of tiles per box, or the area per box. Cartons usually print both.
• Coverage per box: the area one box covers, from the carton.
• Layout and waste allowance: choosing a layout fills in a manufacturer’s rule of thumb for the allowance (see below). You can also type your own allowance; 0% is allowed.
• Spare boxes (optional): whole unopened boxes to keep for repairs.
• Price (optional) and price per: the price as the store quotes it, per square foot, per square meter, per box or, for tile, per tile.

Results update as you type. The Try buttons load a tiled bathroom, the same tile laid diagonally, a room in meters and a floor whose total area is known. To weigh two products, press Save for comparison, change the box size and price, and save again. Copy buying list copies the boxes, coverage and cost as a short list, and Continue in the Sales Tax Calculator carries the materials total over to add tax.

How much flooring do I need?

Measure each rectangle, subtract what won’t be covered, add the waste allowance, divide by the area one box covers and round up to a whole box:

• $A$ is the floor area to cover, in square feet (or square meters).
• $L$ and $W$ are the length and width of each rectangle.
• $w$ is the waste allowance as a decimal (10% is 0.10).
• $c$ is the coverage of one box, from the carton.
• $\lceil\ \rceil$ means round up to the next whole number.

The allowance goes on before rounding. Rounding comes last because you can only buy whole boxes.

Worked example: a living room and hall in 23.8 sq ft boxes

A 15 ft 6 in × 12 ft living room with a 6 × 2 ft stone hearth, and a 10 ft × 3 ft 6 in hall, in rigid-core vinyl plank that comes in boxes of 23.8 sq ft at $59.26 a box.

1. Living room: 15.5 ft × 12 ft = 186 sq ft.
2. Hearth (cut-out): 6 ft × 2 ft = 12 sq ft, which leaves 174 sq ft of living room.
3. Hall: 10 ft × 3.5 ft = 35 sq ft.
4. Floor area: 186 − 12 + 35 = 209 sq ft.
5. With a 10% allowance, AHF’s figure for its click-together rigid-core planks: 209 × 1.1 = 229.9 sq ft.
6. Boxes: 229.9 ÷ 23.8 = 9.66, rounded up to 10 boxes, which cover 238 sq ft.
7. Left over after the allowance: 238 − 229.9 = 8.1 sq ft. In all you buy 29 sq ft more than the floor itself.
8. Cost: 10 × $59.26 = $592.60. That is $2.49 per sq ft of flooring bought, or $2.84 per sq ft of floor once the allowance and the whole boxes are paid for.

Of the 238 sq ft bought, 87.8% goes on the floor, 8.8% is the allowance and 3.4% comes from rounding up to a whole box. Keeping one spare box makes it 11 boxes, 261.8 sq ft and $651.86.

How many boxes of flooring or tile to buy

Buy the fewest whole boxes that cover the floor area plus the allowance. Boxes go up in steps, so a bigger allowance doesn’t always cost more. For the example floor, the calculator’s Boxes at other waste allowances table shows:

Here 5% and 10% buy the same 10 boxes, and so do 15% and 20%. When the area with the allowance is an exact multiple of the box, no extra box is added: 200 sq ft with 10% is 220 sq ft, and 220 ÷ 22 is exactly 10 boxes of 22 sq ft. In binary floating-point arithmetic, 200 × 1.1 ÷ 22 comes out as 10.000000000000002, which a plain round-up turns into 11 boxes; the calculator treats a result within one part in a billion of a whole number, and never more than a thousandth of a box or tile away, as that number.

How much extra to add for waste: straight, diagonal and herringbone layouts

Manufacturers’ instructions give 5% to 30%, depending on the material and the layout. Each figure below is one maker’s rule of thumb for its own products, not a standard, and the Layout choice fills it in for you:

Diagonal and herringbone layouts need more because every row meets the walls at an angle, so more pieces are cut. Not every maker agrees: AHF asks for only 5% on its engineered herringbone (10% laid diagonally). If your product’s instructions give a figure, type it in. The allowance covers cuts and offcuts; it doesn’t fix a room measured too small.

How many tiles do I need (including grout joints)?

Divide the area, with the allowance, by the space one tile takes up with its joint, and round up. Then divide by the tiles per box and round up again:

$L$ and $W$ are the tile’s sides, $g$ the grout joint in the same unit, and $p$ the tiles per box. Each tile covers its own face plus one joint along two sides, because each joint is shared with the neighboring tile.

Example: a bathroom in 12 × 24 in tile. The floor is 9 ft 6 in × 8 ft (76 sq ft), minus a 5 ft × 2 ft 6 in tub (12.5 sq ft) and a 3 ft × 1 ft 9 in vanity (5.25 sq ft), which leaves 58.25 sq ft. With 10%, that is 64.075 sq ft.

1. One tile with a 1/8 in joint: (24 + 0.125) × (12 + 0.125) = 292.52 in², and 292.52 ÷ 144 = 2.0314 sq ft.
2. Tiles: 64.075 ÷ 2.0314 = 31.54, rounded up to 32 tiles.
3. Boxes of 8: 32 ÷ 8 = 4 boxes exactly, with no spare tile.
4. At $1.89 per sq ft, a box of 8 tiles is 16 sq ft of tile, or $30.24, so 4 boxes cost $120.96.

The joint matters most for small tiles. A 1/8 in joint makes each 12 × 24 in tile cover 1.6% more floor; a 1/4 in joint around a 4 × 4 in tile adds 12.9%. In the bathroom, ignoring the joint would give 64.075 ÷ 2 = 32.04, or 33 tiles instead of 32.

Laid diagonally with a 30% allowance, the same bathroom needs 75.725 sq ft, 38 tiles and 5 boxes (40 tiles, 2 of them spare), for $151.20.

How to measure a room with closets, islands or an L shape

Split the floor into rectangles, one row each, and add a cut-out row for anything the new floor won’t go under. An L-shaped room is two rectangles that don’t overlap; a closet that gets the same floor is one more row. A cut-out always comes out of the nearest floor area above it in the list, so the order matters: put the island right below the kitchen. The calculator refuses a cut-out larger than what is left of its area, and a cut-out with no area above it.

If you already know the total, choose Total area and type it in square feet or square meters. In meters, a 4.2 × 3.6 m bedroom is 15.12 m²; with 10% it needs 16.632 m², so 2.2 m² boxes give 16.632 ÷ 2.2 = 7.56, or 8 boxes (17.6 m²). At $27.95 per m² that is $61.49 a box and $491.92 in all.

Comparing prices per box and per square foot

Compare the total for whole boxes, not only the price per square foot, because box size decides how much you buy. Take the example floor (229.9 sq ft with the allowance) and a second plank at $2.39 per sq ft in 32 sq ft boxes ($76.48 a box):

B is cheaper per square foot but costs $19.24 more for this floor, because 8 of its bigger boxes leave 26.1 sq ft over. On a different floor the order can flip. Save each product with Save for comparison to see the difference for your rooms.

Reading the result

• Boxes to buy is the headline, spare boxes included, with the coverage they give.
• Floor area, with waste and left over show the area after cut-outs, the area you buy for, and what remains once the allowance is used.
• For tile, tiles to lay includes the allowance; tiles bought and spare tiles appear when you give the tiles per box.
• Cost shows the total, the price per box, per area and per tile (whichever you didn’t type), and the cost per square foot of floor.
• Where the coverage you buy goes splits the purchase into floor, allowance, rounding and spare boxes.
• Floor area by room lists each area with its cut-outs; download it as a CSV file.
• Boxes at other waste allowances repeats the calculation at 0% to 30% with everything else unchanged.

Assumptions and limitations

• Every area is a rectangle. Curved or angled walls need to be approximated with rectangles that cover them.
• The layout allowances are manufacturers’ rules of thumb for their own products; the instructions for the product you buy come first.
• The coverage per box is used as printed. For tile counted by the piece, each tile takes up (L + g) × (W + g); a price per square foot is applied to the tile faces (pieces × L × W), without the joints.
• When tile is bought by the carton’s area, that area is used as printed. If it counts the tile faces only, each box covers slightly more floor with joints, so the box count errs high.
• The cost covers the boxes only: no sales tax, delivery, underlayment, adhesive, grout, thinset, trim or tools. A store may round each box’s price to the cent.
• Metric and US results agree because 1 ft = 0.3048 m exactly.
• It is an estimate for buying materials, not a quote or installation advice.

Common mistakes

• Rounding before adding the allowance. Add the allowance to the area, then round up once. Adding one box instead of a percentage gives very different allowances: one 23.8 sq ft box is 11.4% of the 209 sq ft example floor but only 2.4% of a 1,000 sq ft floor.
• Reading the allowance as leftover. The allowance is expected to end up as offcuts; the left-over figure is what should remain after that.
• Typing inches as feet. In the US area fields a bare number is feet, so 144 means 144 ft. Type 144 in, or 12. The calculator flags any side over 200 ft.
• Typing a joint as a decimal fraction. An eighth of an inch is 1/8 or 0.125, not 1.8.
• Mixing lots. MSI notes that tiles from different lots can differ in shade, and Crossville explains that calibrated tile is sorted into two to four size groups (calibers). Check that the lot and caliber codes match on every carton, spares included.
• Comparing products on the price per square foot alone. Whole boxes decide the total, as the comparison above shows.