A 12-by-15 foot living room is 180 square feet. That part is easy. What you carry home is not: three vinyl plank floors from the same manufacturer, all cut to the same 7-by-48-inch plank, come 4, 9 or 11 cartons to that one room. The plank is identical. The box is not.
Measure the floor, then stop measuring
Width times length. 12 × 15 = 180 square feet. That is the whole first step for a rectangle.
For an L-shaped room, cut it into rectangles on paper, measure each one, and add them. The only rule that matters is not to count the same strip of floor twice where the rectangles meet. Include closets if you are flooring them, because a closet floor takes planks like any other floor.
Do not subtract a kitchen island or a fixed cabinet run unless the flooring genuinely stops at its base. If you are unsure, leave it in. Under-measuring costs a second trip; over-measuring costs one carton you may want anyway.
The carton is the variable
Three products, one manufacturer, all sold as 7-inch by 48-inch planks:
| Product | Construction | Square feet per carton |
|---|---|---|
| Prime Plank, style 0616V | 2 mm glue-down luxury vinyl | 51.33 |
| Distinction Plus, style 2045V | 7 mm rigid core, attached pad | 23.64 |
| Paladin Plus, style 0278V | 5 mm rigid core, attached pad | 18.91 |
The largest carton holds nearly three times the floor of the smallest one. Nothing on the sample chip tells you that, and the plank size does not predict it: all three are the same 7 by 48 inches. The number you need is printed on the carton and listed in the product's specifications, and it is the only coverage figure that applies to what you are buying.
Your allowance and the rounding are two different things
Add the allowance you have chosen, then divide, then round up to a whole carton. With a 10 percent allowance, 180 square feet becomes 198 square feet to cover:
| Carton | 198 ÷ carton | Cartons to buy | Coverage bought |
|---|---|---|---|
| 51.33 sq ft | 3.86 | 4 | 205.32 sq ft |
| 23.64 sq ft | 8.38 | 9 | 212.76 sq ft |
| 18.91 sq ft | 10.47 | 11 | 208.01 sq ft |
Same floor, same allowance, same plank. Four cartons or eleven.
The 10 percent that changed nothing
Run the same floor with no allowance at all and the counts are 4, 8 and 10 cartons.
So the 10 percent bought exactly one extra carton for the two smaller boxes, and for the 51.33 square foot carton it bought nothing: four cartons either way. That floor was already going to arrive with 25.32 square feet spare, purely because you cannot buy 3.5 cartons. A 10 percent allowance on 180 square feet is 18 square feet. The rounding had already handed you more than that.
This is the slip. "Always add 10 percent" is repeated as though it were a rule that costs you 10 percent. Sometimes it costs a whole carton, sometimes it costs nothing, and the difference is decided by a number you have not looked up yet.
The reverse case matters too. With the 18.91 square foot carton, dropping from 10 percent to none saves one carton and leaves 9.10 square feet spare instead of 28.01. That is a real saving and a real risk, and it is your call, not the calculator's.
Nobody in the chain publishes that 10 percent
We went looking for the source of the rule on the manufacturer's own pages. Shaw's vinyl planning and installation page, read on 2026-09-10, states no waste or overage percentage and does not say how much to buy. It covers technique instead, including the instruction to "undercut door jambs and always work from multiple cartons to achieve a uniform appearance." The flooring overview page, which is where Shaw's retired general-questions address now sends you, carries no percentage either.
That last instruction is worth reading twice if you were planning to open one carton at a time and return the unopened ones. Working from several cartons at once is how installers even out shade variation between boxes, and it is not compatible with keeping cartons pristine for a refund.
So treat the allowance as your decision, made with your own room in mind: how many cuts the layout forces, whether the planks run diagonally, whether you want a spare box on a shelf for the day a chair leg wins.
What this does not cover
The cutting layout, the subfloor, transitions and thresholds, stairs, underlayment, and acclimation are all separate from the count. Attic stock for future repairs is also a separate decision, not part of installation waste: if you want a spare carton in three years, add it deliberately rather than hoping the offcuts survive.
Our flooring calculator does one rectangle at a time, applies the allowance you type, and rounds up to whole cartons. It does not choose a product, compare prices, or judge whether the floor is suitable for the room. The rounding guide shows where each spare square foot comes from.
The whole thing on one line
Floor area × (1 + your allowance) ÷ the square feet printed on your carton, rounded up to the next whole carton.
For this room: 180 × 1.10 = 198, and 198 ÷ 51.33, 23.64 or 18.91 gives 3.86, 8.38 or 10.47, which round to 4, 9 and 11.
One question before you go: do you know what your carton holds? If the answer is "about twenty-something square feet," you are guessing at the one number that decides the order.
Sources
Product figures were read from the manufacturer's pages on 2026-09-10 and are quoted as printed there.
- Shaw Floors, Prime Plank style 0616V colour 00532: "Sq. Ft. Per Carton: 51.33", planks 7 in wide by 48 in long, 2 mm luxury vinyl glue down. https://shawfloors.com/en-us/vinyl/prime-plank-greyed-oak-7-/0616v-00532 (accessed 2026-09-10)
- Shaw Floors, Distinction Plus style 2045V colour 07066: 23.64 square feet per carton, planks 7 in by 48 in, 7 mm rigid core. https://shawfloors.com/en-us/vinyl/distinction-plus-barrel-oak-7-/2045v-07066 (accessed 2026-09-10)
- Shaw Floors, Paladin Plus style 0278V colour 05052: "Sq. Ft. Per Carton: 18.91", planks 7 in by 48 in, 5 mm rigid core. https://shawfloors.com/en-us/vinyl/paladin-plus-fresh-pine-7-/0278v-05052 (accessed 2026-09-10)
- Shaw Floors, vinyl planning and installation page: no waste or overage percentage is stated and no quantity guidance is given; "undercut door jambs and always work from multiple cartons to achieve a uniform appearance." https://shawfloors.com/en-us/plan-and-install/vinyl (accessed 2026-09-10, re-read the same day for any sentence containing a percentage)
- Shaw Floors, flooring overview and comparison page: no waste percentage and no quantity guidance. https://shawfloors.com/en-us/flooring-overview-comparison (accessed 2026-09-10; reached by a permanent redirect from the retired address /product-information/frequently-asked-questions/general-questions, which is why that older address appears in some references)
- Wall Math flooring calculator assumptions (one rectangle, allowance is your input, whole-carton rounding) — own site, checked 2026-09-10. Every carton count and leftover figure in this article was recomputed with the site's calculation code on 2026-09-10.
Numbers are a worked example for one floor. Carton coverage is quoted from the pages above as of the access date; the carton you buy is the source of truth.