Step 1: Measure the floor area
Flooring is sold by the square foot, so that's the number you need. For a rectangular room, area is just length × width measured in feet. A room that's 10 ft by 13 ft is 130 square feet. Measure to the walls, and don't subtract small things like the base of a kitchen island unless it's genuinely large — a little extra under fixed cabinets is cheap insurance.
Few rooms are a perfect rectangle. The reliable approach is to break the space into rectangles: an L-shaped room is two rectangles, a room with a closet or bay is the main rectangle plus the extra. Work out each area separately, then add them together for the total. Doing it section by section is far less error-prone than trying to eyeball one odd shape, and it handles hallways, alcoves, and open-plan rooms cleanly. If you're flooring several rooms with the same product, sum all their areas into one grand total before you go any further.
Step 2: Add a waste factor
You will never use 100% of what you buy. Planks and tiles get cut to fit along walls, and the off-cut is often too short to reuse. Some pieces crack, snap wrong, or get glued down crooked. And you want a few spares boxed in the closet for the day a tile chips or a plank gets water damage — replacing one piece years later from the original batch is the only way to keep the floor seamless. So you always buy more than the bare area:
- 5–10% for a straightforward straight (grid or brick) layout in a simple rectangular room.
- 10–15% for diagonal or herringbone layouts, and for rooms with lots of corners, jogs, and cuts.
- ~15–20% for patterned tile that has to be aligned across the floor, where mismatched pieces can't be used.
When in doubt, round the percentage up rather than down. The cost of one extra box is small next to the cost of a second trip — or a visible patch in a discontinued color.
flooring to buy = floor area × (1 + waste %). Then divide by the square feet per box and round up to the next whole box, because stores sell flooring only by the full box.A worked example
Take a bedroom that's 12 ft × 15 ft. The floor area is 12 × 15 = 180 square feet. With a simple straight layout you'd add a 10% waste factor: 180 × 1.10 = 198 square feet to buy.
Now suppose the laminate you've chosen comes in boxes that each cover 20 square feet. Dividing gives 198 ÷ 20 = 9.9 boxes — which means you need 10 boxes, because you can't buy nine-and-a-bit. Those 10 boxes cover 200 sq ft, leaving you a small, deliberate surplus for repairs. Notice that the rounding step matters: planning for 198 and ordering only 9 boxes (180 sq ft) would leave you short before you even started cutting.
Quick reference: room size to flooring to buy
This chart shows the bare area and the amount to buy at a 10% waste factor for common rectangular rooms. For a diagonal or patterned layout, step up to the higher percentages above.
| Room size | Floor area | Buy at +10% waste |
|---|---|---|
| 8 ft × 10 ft | 80 sq ft | 88 sq ft |
| 10 ft × 12 ft | 120 sq ft | 132 sq ft |
| 12 ft × 15 ft | 180 sq ft | 198 sq ft |
| 14 ft × 16 ft | 224 sq ft | 247 sq ft |
| 16 ft × 20 ft | 320 sq ft | 352 sq ft |
| 20 ft × 24 ft | 480 sq ft | 528 sq ft |
You can run your own numbers — including odd shapes — with the free area calculator, then size the order with the tile calculator or carpet calculator.
Material-specific notes
Tile. Tile is sold by the box, each covering a set square footage. The bare math is the same, but layout drives the waste factor: a straight grid wastes little, while a diagonal set or a running-bond pattern produces more off-cuts. Grout lines don't change how much tile you buy (they're the gaps between tiles), but they do mean you should plan your tile count around the finished module — tile plus grout joint — when you dry-lay the room. For patterned or large-format tile, lean toward the upper end of the waste range. The tile calculator will turn your area and tile size into a box count.
Laminate and luxury vinyl (LVP). These come as planks, packed in boxes by square footage, so you size them exactly like the worked example: area, waste, divide by box coverage, round up. Most floating laminate and LVP floors also need underlayment — a thin foam or cork layer for cushioning and moisture control — which is bought separately by the square foot to match the floor area (some planks have it pre-attached, so check first). Long, straight runs waste little; lots of doorways and angles push you toward 10–15%.
Carpet. Carpet is priced by area too, but it's manufactured on rolls of a fixed width — commonly 12 ft, sometimes 13.5 or 15 ft. Your room has to be covered in strips cut from that roll, and any room wider than the roll needs seams, with extra material to align the pile direction and pattern across the join. That makes real-world carpet waste higher and less predictable than the floor area alone suggests, so let the carpet calculator account for roll width, or get a measured quote from the installer.
Don't forget the extras
Flooring isn't only the field of the floor. Budget for transitions — the strips that bridge doorways and meet other floor types — and for underlayment where the product requires it. Above all, mind the batch: tile and many laminate and vinyl lines vary slightly in color between production runs, so buy all your boxes from the same dye lot at once and check the lot number printed on each box. Carpet has the same issue across rolls. Buying enough the first time, waste factor included, is what spares you from chasing a discontinued or off-color batch later.
The takeaway
Estimating flooring comes down to two honest numbers: the area you're actually covering, and the waste you'll genuinely lose to cuts, mistakes, and spares. Measure carefully, pick a waste factor that fits your layout, and round up to whole boxes from a single batch. Get those right and you'll finish the job with one tidy box left over — exactly what you want.
Frequently asked questions
- How do I calculate the square footage of a room?
- Multiply the room's length by its width in feet. For example, a room 12 ft by 15 ft is 180 square feet. If the room isn't a simple rectangle, split it into rectangular sections, work out the area of each, and add them together. Square footage is the unit flooring is sold in, so this is the number you start from.
- How much extra flooring should I buy for waste?
- Add about 5 to 10 percent for a simple straight layout, 10 to 15 percent for diagonal or herringbone patterns and rooms with many cuts, and around 15 to 20 percent for patterned tile that has to be matched. The extra covers cut-off pieces, mistakes, and a few spare planks or tiles for future repairs.
- Why do I have to round up to whole boxes?
- Tile, laminate, and luxury vinyl are packaged in boxes that each cover a fixed number of square feet, and stores sell them only by the full box. After adding your waste factor, divide the total by the coverage per box and round up to the next whole box, since you can't buy a partial one.
- Do all the boxes need to come from the same batch?
- For tile and many laminate or vinyl products, yes — buy from the same dye lot or production batch and check the lot number on every box. Color and pattern can shift slightly between runs, and a mismatch is very visible across a finished floor. Buying enough at once, including your waste allowance, avoids having to match a new batch later.
This guide is general educational information. Always confirm measurements and product coverage with your supplier or installer before ordering.