How to calculate flooring
Flooring is sold by area, but you buy it in whole boxes. Measure each room wall to wall in feet, multiply length by width and add the rooms together. Then add a waste allowance for the cuts at the walls and round the box count up. Measure closets, hallways and each leg of an L-shaped room as separate rectangles, so nothing gets missed.
Example: a living room of 12 by 15 ft plus a closet of 4 by 6 ft is 180 + 24 = 204 square feet. With 10 percent waste that is 224.4 square feet. Laminate boxes of 22 square feet give 224.4 ÷ 22 = 10.20, so you buy 11 boxes, which cover 242 square feet. Underlayment rolls of 100 square feet: 204 ÷ 100, rounded up to 3 rolls. At $2.50 per square foot the flooring costs 11 × 22 × $2.50 = $605.00, because you pay for full boxes.
Waste and coverage by flooring type
- Laminate: typical waste 10 percent, boxes of about 20 to 24 square feet. Needs underlayment unless a pad is attached.
- Vinyl plank (LVP): typical waste 10 percent, boxes of about 20 to 30 square feet. Many planks have an attached pad and need no extra underlayment.
- Hardwood, solid or engineered: typical waste 10 percent laid straight, about 15 percent on the diagonal. Boxes often hold around 20 square feet.
- Carpet: typical waste 10 percent. In the US it is sold by the square yard from rolls 12 ft wide, so the calculator shows square yards and the roll length instead of boxes.
Laying planks on the diagonal adds about 5 percent more waste, since every row starts and ends with an angled cut. Ceramic and porcelain tile work differently, with grout joints and tiles per box, so use the tile calculator for those floors.
Boxes for common room sizes
| Room | With 10% waste | 22 sq ft boxes | 24 sq ft boxes | Carpet sq yd |
|---|---|---|---|---|
| 10 × 10 ft (100 sq ft) | 110.0 sq ft | 5 | 5 | 12.2 |
| 12 × 12 ft (144 sq ft) | 158.4 sq ft | 8 | 7 | 17.6 |
| 12 × 15 ft (180 sq ft) | 198.0 sq ft | 9 | 9 | 22.0 |
| 14 × 16 ft (224 sq ft) | 246.4 sq ft | 12 | 11 | 27.4 |
| 20 × 20 ft (400 sq ft) | 440.0 sq ft | 20 | 19 | 48.9 |
Each row is one room on its own. When you floor several rooms with the same product, add the areas first and round up once, which often saves a box.
Underlayment and cost
Underlayment rolls are counted from the floor area without the waste allowance, because offcuts are small and the seams are butted or taped. Typical foam rolls cover 100 square feet. The flooring cost is the number of boxes times the price per box, or the area in those boxes times the price per square foot. Installation is usually quoted per square foot of floor, so the calculator multiplies it by the floor area. Ask your installer whether removal of the old floor, trim and transitions are included.
How to use the flooring calculator
- 1Choose US or metric units and enter the length and width of each room. Add closets, hallways and each part of an L-shaped room as their own rows.
- 2Pick laminate, vinyl plank, hardwood or carpet. The calculator fills in a typical waste allowance, coverage per box and underlayment setting, which you can change.
- 3Switch the layout to diagonal if you lay planks at an angle, and type the coverage per box from the carton of the product you plan to buy.
- 4Turn underlayment on or off and set the area one roll covers.
- 5Enter the price per square foot or per box, plus the underlayment and installation prices if you have them, then copy the result for the store.
Frequently asked questions
How many boxes of flooring do I need?
Multiply the square feet of the room by 1.10 for 10 percent waste, divide by the coverage per box printed on the carton and round up. A 12 by 15 ft room is 180 square feet, 198 with waste, so with boxes of 22 square feet you need 9 boxes. Add every room, closet and hallway first, then round up once for the total.
How much extra flooring should I buy for waste?
About 10 percent is typical for laminate, vinyl plank and hardwood laid straight. Laid on the diagonal, plan for about 15 percent, because every row ends in an angled cut. Small rooms, closets and rooms with many corners waste more. Keep one leftover box for repairs, since the same color and batch can be hard to find later.
How many square yards of carpet do I need?
Divide square feet by 9. A 12 by 15 ft bedroom is 180 square feet, or 20 square yards, and about 22 square yards with 10 percent waste. In the US carpet usually comes in 12 ft wide rolls, so rooms wider than 12 ft need a seam, and an installer may measure a little more than the plain floor area.
Do I need underlayment under vinyl plank flooring?
Not when the planks have an attached pad, which many vinyl plank products do. An extra foam layer under them can make the click joints flex and may void the warranty. Laminate and floating engineered hardwood usually need underlayment unless it is pre-attached. Typical rolls cover 100 square feet, and over concrete you may also need a vapor barrier.
How many square feet are in a box of laminate?
Typical laminate boxes cover about 20 to 24 square feet, vinyl plank boxes about 20 to 30 and hardwood boxes often around 20. Thicker planks mean fewer per box. The exact coverage per box is printed on the end of the carton, so enter that number for an accurate box count.