Flooring is sold in cartons that cover a fixed number of square feet, and you can rarely buy a partial box. This calculator takes the floor area, adds an allowance for cuts and defects, divides by the coverage printed on the carton and rounds up to whole boxes. It also estimates underlayment rolls and the cost of the flooring you actually pay for, which is always a little more than the floor itself.
How to use the flooring calculator
- Choose US or Metric units.
- Enter the room’s length and width, or switch to Known area if you have already added up several rooms.
- Set the waste percentage for your layout.
- Enter the coverage per box from the carton label.
- Optionally enter the price per square foot (or square meter).
- Leave Add underlayment ticked to estimate rolls, and enter the roll coverage.
Flooring formulas
Because stores price flooring per square foot but sell it by the box, the cost is based on the full boxes you buy rather than the floor area.
Worked example: a 15 × 12 ft living room
Area: 15 × 12 = 180 ft². With 10% waste: 180 × 1.1 = 198 ft².
Boxes of 20 ft²: 198 ÷ 20 = 9.9 → 10 boxes (200 ft²).
At $2.79 per ft²: 200 × $2.79 = $558.00.
Underlayment: 180 × 1.05 = 189 ft² → 2 rolls of 100 ft². Perimeter for baseboard: 54 ft.
Typical waste by layout
| Layout or room | Extra to buy |
|---|---|
| Large open rectangle, straight lay | 5–7% |
| Typical room, straight lay | 10% |
| Many corners, closets or doorways | 12–15% |
| Diagonal (45°) | 15% |
| Herringbone or chevron | 15–20% |
Waste comes from cutting the last plank in every row, trimming around door jambs and cabinets, and culling boards with chipped edges or poor color. Planks that are longer than average leave longer offcuts, which can often start the next row, so long-plank products in plain rectangles are the most efficient.
Buying tips
- Check the lot numbers. Colors vary between production runs. Buy every box at once and confirm the cartons share a lot or run number.
- Mix boxes as you go. Open three or four cartons and pull planks from each so slight shade differences spread across the floor.
- Keep spares. One leftover box, stored flat in the house, makes future repairs much easier, since a product may be discontinued within a few years.
- Plan transitions and trim. Doorways between different floors need transition strips, and floating floors need an expansion gap at the walls, which baseboard or quarter-round covers. The perimeter in the results is a starting point for trim; subtract door openings.
- Prepare the subfloor. Most floating floors need the subfloor flat to within about 3/16 inch over 10 feet (check your product), so budget for leveling compound in older homes.
Related calculators
For tile floors, the tile calculator accounts for grout joints and tiles per box. Carpet is sold off wide rolls rather than in boxes, so use the carpet calculator for bedrooms and stairs. If the room is an L-shape or has a bay, total its parts with the square footage calculator, then enter the sum as a known area here.
Frequently asked questions
How much extra flooring should I buy?
Plan on about 10% for a simple room with planks laid straight. Use 7% only for large, open rectangles, 15% for diagonal layouts or rooms with many corners and doorways, and 15–20% for herringbone or chevron patterns.
How many boxes of flooring do I need for 500 square feet?
Add 10% for waste to get 550 ft², then divide by the coverage on the carton. With 22 ft² per box that is exactly 25 boxes; with 20 ft² per box it is 27.5, so you would buy 28.
Do closets count in the flooring area?
Yes. Measure closets, alcoves and the space under appliances that will sit on the floor, such as a refrigerator or range, if the flooring runs underneath. Measure each piece as a rectangle and add the areas.
Do I need underlayment under vinyl plank or laminate?
Laminate almost always goes over a foam or cork underlayment. Many vinyl plank products have a pad attached and must not get a second cushion layer. Over concrete, most makers call for a moisture barrier. Follow the installation instructions for your product, because the wrong underlayment can void the warranty.
Why do flooring makers say to acclimate the boxes?
Wood and laminate expand and shrink with temperature and humidity. Leaving the boxes in the room for the period the maker specifies, often 48 hours or more, lets the planks adjust before installation so gaps and buckling are less likely.