Flooring Calculator: Laminate and Plank Boxes Needed
Enter the room size, the coverage printed on one box and a waste percentage. You get the boxes to buy and the surplus left over. After switching units, re-enter your measurements.
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Formula
room area = length × width
area with waste = room area × (1 + waste%)
boxes = round up (area with waste ÷ coverage per box)
left over = boxes × coverage per box − room area
Worked example
A 15 ft by 12 ft room, boxes of 20 sq ft, 10% waste:
- Room area: 15 × 12 = 180 sq ft.
- With waste: 180 × 1.1 = 198 sq ft.
- Boxes: 198 ÷ 20 = 9.9, rounded up to 10 boxes, covering 200 sq ft.
- Left over: 200 − 180 = 20 sq ft.
In metric, a 5 m by 4 m room with 2.2 m² boxes needs 20 × 1.1 ÷ 2.2 = 10 boxes exactly.
Assumptions
- The room is one rectangle; closets, alcoves and stairs must be added separately.
- Coverage per box is the figure printed on the carton, not the plank count.
- Waste of 10% suits straight lay; use about 15% for diagonal layouts.
- The default coverage of 20 is in square feet; when you switch to metric, enter the box coverage in square metres.
Frequently asked questions
How many boxes of laminate do I need for a 15 by 12 ft room?
The room is 180 sq ft. Add 10% waste for 198 sq ft and divide by 20 sq ft per box: 9.9, so you buy 10 boxes, which cover 200 sq ft and leave 20 sq ft spare.
How much waste should I allow for flooring?
About 5 to 10% for straight lay in a simple room, 10 to 15% for diagonal layouts or rooms with many corners. At 15%, the same 180 sq ft room needs 207 sq ft, which is 11 boxes.
Where do I find the coverage per box?
It is printed on the carton and the product page, usually as sq ft or m² per box, such as 20 sq ft or 2.2 m². Use that figure rather than counting planks, as it accounts for the tongue and groove overlap.
Does the calculator allow for closets and alcoves?
No, it treats the room as one rectangle. For an L-shaped room or closets, work out each rectangle and add the areas, or enter an equivalent length and width that gives the total area.