How to use this calculator
Measure the room’s length and width at the longest points and multiply them; for L-shaped rooms, split the floor into rectangles and add the areas. Enter the total with the coverage printed on the box (usually 18–24 ft² for laminate and luxury vinyl plank, 20–30 ft² for engineered wood). The waste allowance defaults to 10%, the figure most manufacturers recommend for a straight lay.
Raise the allowance to 15% for diagonal or herringbone patterns or rooms with many corners and doorways. Working backwards, enter the number of boxes you have to see the floor area they will cover after waste.
The formula
- A
- floor area
- w%
- waste allowance
- A_buy
- area to buy (incl. waste)
- c
- coverage per box (from the label)
- N
- boxes needed
Worked example
A 12 × 15 ft living room is getting laminate planks sold in boxes that cover 20 ft² each.
- Floor area = 12 × 15 = 180 ft².
- Add 10% for cuts: 180 × 1.10 = 198 ft².
- Boxes = 198 ÷ 20 = 9.9, rounded up to 10 boxes.
Buy 10 boxes (200 ft²). Keep one unopened box if the store accepts returns — it is handy for future repairs.
Typical waste allowances
| Layout | Allowance |
|---|---|
| Straight lay, simple rectangular room | 5–10% |
| Straight lay, many doorways or closets | 10–12% |
| Diagonal lay | 15% |
| Herringbone or chevron | 15–20% |
Assumptions and limits
- Coverage per box is the manufacturer’s figure for the face area of the planks, without the tongue.
- Leave the expansion gap the manufacturer specifies at walls (typically ¼–⅜ in); it does not materially change the quantity.
- Underlayment, transitions and baseboard are not included.
Frequently asked questions
How much extra flooring should I buy?
About 10% for a straight lay in a normal room, 15% or more for diagonal and patterned layouts. It covers cut-offs, defective boards and future repairs.
Should I include closets?
Yes, if the flooring runs into them. Measure them as separate rectangles and add them to the total area.
Can I return unopened boxes?
Most stores accept unopened boxes, but check first. Keeping one spare box from the same production lot makes color-matched repairs possible later.
Sources
- National Wood Flooring Association — Installation and technical resources
- NIST Handbook 44, Appendix C — Units of area
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