Formula
Net area is the rooms minus the subtract rows, and it does not go below zero. Order area is the net times one plus waste. Boxes are the order divided by the coverage on the carton, rounded up. Purchased area is boxes times that coverage. Leftover is purchased minus the order.
net = rooms − subtract
order = net × (1 + waste ÷ 100)
boxes = ceil(order ÷ coverage)
carpet sq yd = order ÷ 9
layout sq yd = shorter run × roll width ÷ 9
Carpet also tries both ways the roll can face. Strips are the room side across the roll, rounded up, times the other side. The shorter of the two runs is the one shown. Square yards from that layout are the linear feet times the roll width, divided by 9, then rounded up. Seams and a pattern match add more than this. Underlayment uses the net area, plus its own waste, divided by the roll. Material cost uses purchased plank area. Labor uses net area. Carpet cost uses the rounded layout yards.
Worked examples
12 × 15, 10 × 11, and a 4 × 6 closet. 314 sq ft. At 10 percent, order 345.4 sq ft. A 20 sq ft box is 18 boxes, 360 sq ft purchased, 14.6 sq ft left over. Herringbone at 20 percent is 19 boxes. Diagonal at 15 percent is 19 boxes. Underlayment at 5 percent is 4 rolls of 100 sq ft. At $3.49 a square foot and $2 labor, material is $1,256.40 and labor is $628.00, total $1,884.40 before any underlayment price.
Carpet, 13 × 15 ft, 12 ft roll. Two strips the long way is 26 linear feet, 312 sq ft, 34.67 sq yd, so order 35. The area method at 10 percent is 23.83 sq yd. The gap is the unused width of the roll. A 12 × 15 room the other way is one strip, 15 linear feet, 20.00 sq yd.
4 × 5 m, 10 percent, 2.2 m² per box. 22 m², 10 boxes, no leftover.
Reference
Planning waste. The installation guide can call for a different percent.
| Layout | Starting waste |
|---|---|
| Straight lay | 10% |
| Diagonal | 15% |
| Herringbone or chevron | 20% |
Questions
How do I calculate square footage for flooring?
Multiply length by width for each rectangle, then add the rectangles. A 12 × 15 room is 180 sq ft. An L-shaped room is two rectangles. Subtract islands, built-ins, and a hearth. The three rooms on this page are 180 + 110 + 24 = 314 sq ft.
How much extra flooring should I buy?
Straight lay starts at 10 percent. A diagonal starts at 15. Herringbone or chevron starts at 20. A narrow closet or a room full of angles can need more. The carton and the installation guide win.
How many boxes of flooring do I need for 500 sq ft?
At 10 percent waste the order is 550 sq ft. A box that covers 20 sq ft is 550 ÷ 20 = 27.5, so you buy 28 boxes, 560 sq ft. Keep one spare box from the same lot for repairs.
How do I convert square feet to square yards for carpet?
Divide by 9. One square yard is a 3 × 3 ft square. 195 sq ft with 10 percent waste is 214.5 sq ft, which is 23.83 sq yd. A 12 ft roll often uses more than that, because the leftover strip is still on the roll.
Why does carpet need more than the room area?
Broadloom is 12, 13.5, or 15 ft wide. A 13 ft room on a 12 ft roll needs two strips. This page tries both directions and keeps the shorter run. Seams, pattern match, and a stair still add more. CRI 105 is the installation standard for those seams.
Do I need underlayment for vinyl plank?
Only if the plank does not already have a pad. Many LVP products have the pad attached. A separate roll here defaults to 100 sq ft and 5 percent waste, on the net area. The product sheet says which pad, if any, is allowed.
How much does it cost to install LVP per square foot?
Type your own material price and your own labor price. Material is charged on the area you purchase, full boxes. Labor is charged on the net area you install. This page does not publish a national price.
Sources
- North American Laminate Flooring Association installation guidelines, and the plank maker’s own sheet, for acclimation, attached pad, and the waste the layout actually needs. The 10, 15, and 20 percent figures are planning starts on this page.
- Carpet and Rug Institute, CRI 105, the residential carpet installation standard, for seams and pattern match. Roll widths of 12 ft, 13 ft 6 in, and 15 ft are the common broadloom goods. The shorter-run layout is this page’s estimate.
- NIST SP 811. One square yard is 9 square feet. One square metre is 10.7639104167 square feet, from 0.3048 m per foot.