How to use this calculator
Put the room in as feet and the plank in as inches. Most laminate is 7 to 8 inches wide and 48 inches long, with cartons covering 18 to 22 square feet. Set the coverage from the label, not from memory: it changes between widths inside the same product line.
Leave the pattern on plank stagger. The plan will draw each row, randomise the starting length within the manufacturer's offset rule, and show you which planks have to be cut.
Expansion gaps change your numbers
Laminate is a floating floor over a fibreboard core, and that core moves with humidity. Every manufacturer requires a gap of a quarter inch at every vertical surface — walls, door jambs, pipes, the hearth, the island. In a 12 by 14 room that removes about half a square foot of finished floor, which is nothing, but it changes the cut list on the first and last row.
What actually costs you material is the rip. If the room is 144 inches wide and the plank is 8 inches, the room is 18 planks exactly, and the last row would be a full plank with no gap — which is not allowed. So you rip the first row to about 7 1/2 inches and the last to about 7 3/4. Two long thin strips of waste, every time.
On a run longer than 26 feet in either direction you need an expansion joint in the middle of the floor, with a T-moulding over it. That is not optional and it is not a defect; it is how a floating floor survives a season.
AC ratings and thickness
The AC rating is an abrasion class, from AC1 to AC5. AC3 handles a normal family home. AC4 is worth the extra 40 cents a square foot in a kitchen, an entry or anything you are renting out. AC5 is commercial and a waste of money in a house.
Thickness is 7, 8, 10 or 12 mm. Thicker planks feel more solid underfoot and bridge small subfloor imperfections better, but thickness has no relationship to wear resistance. An 8 mm AC4 outlasts a 12 mm AC3 every time.
The edge profile is the other thing to check on the sample before you order. A square edge reads as one continuous surface and hides a slightly uneven subfloor; a painted or embossed bevel reads as individual planks and collects dust in the groove. Neither is better, but they look completely different once a whole room is down, and a display board of six planks does not show it. Ask for a full plank to take home if you can.
Underlayment
If the plank has no attached pad you need underlayment, and you buy it in the same square footage as the floor plus about 5% for the overlaps at the seams. Over a concrete slab you need a 6 mil vapour barrier under or built into the pad — laminate over a slab with no barrier will swell from the bottom within a year and there is no repair.
Do not double up. Attached pad plus a separate pad is the most common warranty void in the category, because the extra give flexes the click joints until they fail.
If the floor is going above a bedroom or in an apartment, the underlayment also carries the sound rating. Look for the IIC and STC figures on the roll: IIC 60 or above is the usual condo requirement, and many buildings write a minimum into the bylaws. A 2 mm foam at IIC 51 costs half as much as a 3 mm rubber-backed pad at IIC 66, and only one of them will get past a building manager.
Common mistakes
- No acclimation. 48 hours in the room, cartons flat and unopened, at living temperature. This is the single most skipped step and the single most common cause of gapping.
- Wet mopping. Laminate is not waterproof, whatever the box says. Water through a seam swells the core permanently. If the room has a floor drain or a toilet, consider vinyl plank instead — the trade-offs are laid out in LVP vs laminate.
- Nailing the transition strips through the floor. The floor has to float. Fasten the track to the subfloor in the gap, not through the plank.
- Pattern repeat. Cheap laminate has four or six printed faces and they repeat. Pull planks from three cartons at once or you will see the same knot four times in one row.
- Under-ordering the waste. Ten percent is the floor, not the ceiling — read flooring waste factor before you place the order.