EstimatorKitLaminate, vinyl plank and wood
Flooring by the carton, and how the rows land
Flooring is bought in whole cartons, and from a room and a product this counts them — laminate, vinyl plank, engineered or solid — along with the underlayment rolls under them and a transition stick for each doorway. It also lays the rows out: how many full ones fit across the run, how wide the strip against the far wall comes out, and whether that strip is too narrow to click in — the layout question that decides how a floor looks and that a square-footage total cannot answer.
- 4 plank products
- Last-row rip check
- Underlayment and transitions
0.25 in expansion gap — a working figure for laminate, not one maker's; the installation sheet in the box sets the real gap. Floats, so it needs underlayment and a transition past 40 ft of run, also a working figure.
Rows cross the run, so this is what decides the last-row rip. Nailed-down boards also have to cross the joists.
Whole boxes, because that is how it is sold
16 boxes
- Those boxes cover
- 320 sq ft
- Floor, bare
- 293 sq ft
- With 8% for cuts
- 317 sq ft
- Spare after the last row
- 3.2 sq ft
- Underlayment
- 3 rolls
- Transition sticks
- 2 × 78 in
How the rows come out
Across 13' 4" of room, less 0.5 in of expansion gap, you get 21 full rows and a final strip 2" wide.
That last strip is under 2 in, which is too narrow to hold a click joint or to sit flat. Rip the first row down as well and run both at 4 3/4" — the room looks balanced and neither edge is a sliver. Decide this before the first board goes down; it cannot be fixed at the far wall.
Each row takes 6 planks along 22', leaving 2' 1/2" at the end. That offcut is longer than the 8 in minimum stagger this page works to, so it starts the next row and nothing is thrown away.
The 8% allowance is on top of the bare 293 sq ft, not folded into it, so you can hold a quote against either figure. Boxes then round up once, at the end — which is why the spare comes out at 16% of a box rather than a convenient number.
Cartons, and where the last row lands
Plank flooring is priced per square foot and sold per carton, and those two facts do not meet in the middle. A carton holds somewhere between 18 and 30 square feet depending on plank thickness and length, the figure is stamped on the carton and it differs for every product on the aisle, which is why a calculator that stops at “you need 312 square feet” has stopped one step early. The rounding should happen exactly once, against that carton figure, at the end: rounding the room up, then the waste up, then the cartons up compounds three cushions into a stack of boxes nobody asked for. What is worth an extra carton on purpose is the run number on the label, because flooring is printed and milled in batches and a board pulled from next year’s batch will not match the floor it is patching. Tile has the same problem under a different name — the shade and caliber printed on its carton.
The part almost no flooring calculator touches is where the rows land. Take the room dimension across the run, subtract the expansion gap at both walls, divide by the plank width, and the fraction left over is the strip that will sit against the far wall for the life of the floor. If it comes out under about 2 in it is a problem, not a detail: there is not enough tongue left to lock, the piece flexes as you lever it home, and the eye reads it as a mistake. The fitter’s answer is to take the shortfall and share it — rip the first row down so the first and last rows are the same width — and it only works if the decision is made before the first board is laid. The end joints have their own rule running the other way: stagger them by the minimum the installation sheet gives — this page works to 6 in on vinyl plank and solid strip, 8 on laminate and 12 on engineered plank — which is exactly why the offcut from the end of one row is usually the piece that starts the next, and why a room whose length divides evenly into the plank length wastes more than one that does not.
Everything above assumes the floor can move, and a floating floor is a single rigid panel the size of the room. That is where the gap comes from, it is why a long click floor needs a T-molding to split it into two fields once it passes the run its installation sheet allows — this page flags 30 ft for vinyl plank and 40 for laminate, working figures the sheet in the box overrides — and it is why the subfloor has to start flat to the tolerance that sheet prints, which is flatter than most houses. Transition pieces come as uncut 78 in and 94 in sticks, one continuous piece per opening, because a spliced threshold in a doorway is the first thing to lift. Where the space underneath is a crawlspace or an unheated garage, the floor above it is also a thermal boundary and the insulation calculator covers the batts that go between the joists. If the room is getting broadloom instead, the arithmetic changes shape entirely — carpet is cut from a fixed-width roll rather than counted in boxes, and the carpet calculator works in seams instead of rows.
Flooring questions
How many boxes of flooring do I need?
Divide the room area plus its waste allowance by the square feet in one carton, then round up once — and buy one carton beyond that. The reason for the extra is the run number stamped on the label: boards are milled and printed in batches, and a carton bought next year will differ enough in tone that a patched board reads as a patch. Cartons are not returnable once opened in most stores, so the spare costs the price of a box and saves the price of a floor.
Which direction should the planks run?
Along the longest dimension of the room and away from the main window, unless the floor is nailed down, in which case the joists decide. Solid boards fastened through the subfloor have to run perpendicular to the joists so each board is fixed at multiple points; laying them parallel means every board sits in a single bay and the floor moves with the subfloor. Floating floors have no such constraint, so the choice is about seams, which disappear when the plank length runs with the light rather than across it.
The last row comes out two inches wide — is that a problem?
Yes, and the fix is at the opposite wall. A strip under about 2 in has almost no tongue left to click into, snaps while you are levering it in and looks like a mistake even when it survives. Take the shortfall and split it across the first and last rows: if the leftover is 1.5 in and the plank is 7.5, rip both edge rows to 4.5 in and the room reads as deliberate. This has to be decided before the first row is laid, because the first row sets every row after it.
How big does the expansion gap have to be?
Whatever the installation sheet in the box says. This page starts from a quarter inch for laminate and rigid-core vinyl and half an inch for a floating engineered floor, working figures rather than one maker's, and for solid hardwood the NWFA guideline is a space equal to the thickness of the board — 3/4 in for a standard strip. The gap is not a tolerance for bad cutting: a floating floor is one rigid panel the size of the room, and it grows and shrinks across its width with the season. Pinch it at a wall, a pipe or a door casing and it has nowhere to go but up, which is what peaking is.
Do I need underlayment under vinyl plank?
Only if the plank does not already have a pad attached, and doubling up is worse than none. An attached pad plus a foam roll gives the click joints too much to sink into; the locking edges work against each other every time somebody walks across, and they wear out. Where a separate roll is called for, it comes as foam or as a 2-in-1 with a vapor barrier built in, and on a concrete slab the vapor barrier is not optional at any thickness. This page counts it in 100 sq ft rolls; count with the coverage printed on the roll you buy.