Flooring & Tile Calculator
Multiply the room's length by its width, then add about 10% for cuts and waste. A 12 × 15 ft room is 180 sq ft; with 10% extra that's 198 sq ft, or 10 boxes of flooring at 20 sq ft per box, or 198 tiles of 12 × 12 inches.
For an L-shaped room, split it into rectangles and add the results.
Flooring needed
198 sq ft
Floor area
180 sq ft
Boxes
10
Tiles
198
Show the math
- 1
Floor area = length × width
15 × 12 = 180 sq ft
= 180 sq ft
Read the steps as text
- Floor area = length × width. 15 × 12 = 180 sq ft
- Add 10% for cuts and waste. 180 × 1.1 = 198 sq ft Pieces are cut to fit at walls and corners, and some break. 10% is typical; use 15% for diagonal layouts or patterns.
- Boxes to buy. 198 ÷ 20 sq ft per box = 9.9 → 10 boxes Rounded up, since you can't buy part of a box. Keep a spare for future repairs.
- Tiles to buy. 12 × 12 in = 1 sq ft each → 198 ÷ 1 = 198 tiles Tile size in inches is divided by 144 (12 × 12) to convert square inches to square feet.
Measuring and the waste allowance
Measure the room's length and width at their longest points and multiply to get the area. For an L-shaped or irregular room, split it into rectangles, work out each one and add them together.
Always buy more than the exact area. Boards and tiles have to be cut to fit along walls and around doorways, and some pieces break or have defects. 10% extra is the usual allowance; use 15% or more for diagonal or herringbone patterns, or rooms with lots of corners.
Boxes, tiles and cost
Flooring is sold by the box, with the coverage printed on it. Divide the area including waste by the coverage per box and round up. For tiles, the calculator divides the area by the size of one tile: in US units, length × width in inches ÷ 144 gives square feet per tile.
If you add a price, the cost is based on the full boxes you'll buy rather than the exact area. Keep a spare box after installation, since matching the same batch years later can be difficult.
Frequently asked questions
- How much extra flooring should I buy?
- About 10% for a standard straight layout, and 15% or more for diagonal or patterned layouts and awkwardly shaped rooms.
- How many 12 × 12 tiles do I need for 100 square feet?
- Each tile is 1 sq ft, so 100 tiles for the exact area, or 110 with a 10% waste allowance.
- How do I measure an L-shaped room?
- Split it into two rectangles, find the area of each and add them. You can run the calculator twice and add the box counts.
- Does this include underlayment or grout?
- No. Underlayment usually covers the same area as the floor; grout and adhesive coverage is printed on their packaging.