How much flooring do I need?
Multiply the room length by its width, add a waste allowance for cuts, then divide by the square feet in one box and round up. A 15 × 12 ft room is 180 sq ft; with 10% waste you need 198 sq ft, which is 10 boxes of 20 sq ft flooring.
Worked example: a 15 × 12 ft living room
- Floor area: 15 × 12 = 180 sq ft.
- Add 10% waste: 180 × 1.10 = 198 sq ft.
- Boxes: 198 ÷ 20 = 9.9, rounded up to 10 boxes.
Flooring needed by room size
With 10% waste and boxes that cover 20 sq ft.
| Room | Floor area | With 10% waste | Boxes |
|---|---|---|---|
| 10 × 10 ft | 100 sq ft | 110 sq ft | 6 |
| 12 × 12 ft | 144 sq ft | 158.4 sq ft | 8 |
| 12 × 15 ft | 180 sq ft | 198 sq ft | 10 |
| 14 × 16 ft | 224 sq ft | 246.4 sq ft | 13 |
| 16 × 20 ft | 320 sq ft | 352 sq ft | 18 |
| 20 × 20 ft | 400 sq ft | 440 sq ft | 22 |
How much extra flooring should I buy?
Waste comes from cuts at walls and doorways, damaged planks and pattern matching. Diagonal and herringbone layouts produce more offcuts than straight rows.
| Flooring | Simple layout | Complex layout | Diagonal or pattern |
|---|---|---|---|
| Hardwood | 10% | 12–15% | 15% |
| Laminate | 7% | 10% | 10–12% |
| Luxury vinyl plank or tile | 5% | 7–10% | 10% |
| Ceramic or porcelain tile | 10% | 15% | 20% |
How the calculator works
Floor area = length × width
Flooring to buy = floor area × (1 + waste %)
Boxes = flooring to buy ÷ coverage per box, rounded up
For an L-shaped room, split it into rectangles, run each one and add the boxes together. Include closets you plan to floor, and leave out areas under fixed cabinets.
Frequently asked questions
How much extra flooring should I buy?
About 10% for a standard room with straight rows. Simple rooms with vinyl plank can use 5% to 7%, while diagonal or patterned layouts need 15% or more.
How many boxes of flooring do I need for a 12 × 12 room?
A 12 × 12 ft room is 144 sq ft. With 10% waste that is 158.4 sq ft, so with boxes of 20 sq ft you need 8 boxes.
Should I keep leftover flooring?
Yes. Keep at least one spare box for repairs, because planks from a later production run may not match the color exactly.
Does the calculator work for carpet?
Use it for the square footage, then check how your carpet is sold. Carpet usually comes on rolls of fixed width, so seams and roll width also affect how much you buy.
Sources
- Flooring Clarity, How Much Extra Flooring To Buy
- Word of Mouth Floors, How Much Extra Flooring Should You Order?