Flooring calculator
Add up the rooms, choose the waste factor for your layout, and enter the coverage printed on the box. The calculator tells you how many boxes to buy, how much underlayment you need, and what it all costs.
How the flooring calculator works
Flooring is sold by the box, and each box covers a set number of square feet that is printed on the label. The calculator totals your floor area, adds a waste percentage for cuts along walls and around obstacles, then divides by the box coverage and rounds up to whole boxes. Because you cannot buy a partial box, it also shows the leftover you will have for future repairs.
Underlayment is estimated at one 100 square foot roll per 100 square feet of floor, with no waste factor since rolls are easy to piece together. Skip it for tile, glue-down vinyl, or planks that come with a pad attached.
Formula
area = length × width × rooms + extra
boxes = area × (1 + waste) ÷ coverage per box, rounded up
Example: a 15 × 12 ft living room plus a 40 sq ft closet is 220 sq ft. With 10 percent waste you need 242 sq ft. If each box covers 20 sq ft, that is 12.1 boxes, so buy 13 boxes, or 260 sq ft, leaving 40 sq ft spare.
How much waste to allow
- 5 percent is enough for a rectangular room with planks laid parallel to the long wall and no obstructions.
- 10 percent covers most homes with a few doorways, closets, and a kitchen island.
- 15 percent for diagonal or herringbone layouts, which waste a triangle at every wall.
- 20 percent for large-format tile, where one broken or badly cut piece costs several square feet.
- Sheet vinyl and carpet come in 12 ft rolls, so waste depends on how the room divides into 12 ft widths rather than a percentage.
Finishing the walls at the same time? The paint calculator uses the same room measurements.
Common questions
How many boxes of laminate flooring do I need for 500 square feet?
About 28 boxes if each covers 20 sq ft, after adding 10 percent waste for 550 sq ft. Check your box label, since coverage ranges from 18 to 30 sq ft depending on plank size.
How much extra flooring should I buy?
10 percent extra is the standard allowance for cuts and mistakes. Go to 15 percent for diagonal patterns or rooms with many angles. Return unopened boxes if the store allows, but keep one for repairs.
How do I measure a room for flooring?
Measure the longest length and widest width in feet and multiply them. For L-shaped rooms, split the space into rectangles, calculate each, and add them together. Include closets and the space under door thresholds.
Do I need underlayment under vinyl plank flooring?
Only if the planks do not have a pad attached and the manufacturer calls for it. Many luxury vinyl planks include a pad and go straight over a clean, flat subfloor. On concrete, a vapor barrier is usually still required.