Laminate Flooring Calculator

Calculate how many boxes of laminate flooring you need for a room, plus the rolls of underlayment and the quarter round or trim to finish the edges.

By CalcBuilt Editorial TeamUpdated September 9, 2026Formulas checked against manufacturer specs, see how we calculate.

Quick answer: To find how much laminate you need, multiply room length by width, add 10% for waste, and divide by the coverage per box; underlayment is the floor area divided by 100 sq ft per roll, and trim is the perimeter minus 3 ft per doorway. A 12 x 10 ft room needs 132 sq ft of laminate including 10% waste, which is 7 boxes at 20 sq ft per box, plus 2 rolls of underlayment and 41 ft of quarter round.

Your measurements

Plan view from above: area is length times width.

Room lengthftRoom widthftExtra area (closets, hallway)sq ftDoorwaysEach doorway is deducted as 3 ft from the trim length.Waste allowance%10% for a rectangle; 15% for diagonal layouts, L-shaped rooms and many jambs. Waste is mostly the last plank in each row, so 4 ft planks in a 10 ft room waste more than in a 12 ft room.Coverage per boxsq ftPrinted on the box. Most laminate boxes cover 18 to 24 sq ft.UnderlaymentNever put a foam roll under attached-pad planks; it voids the warranty and makes the joints spongy. Over concrete you still need 6 mil poly unless the pad has a vapor barrier built in.Price per sq ft (optional)$/sq ft

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Laminate to buy132 sq ftAll results

Results

Laminate to buy: 132 sq ft; 120 sq ft floor area plus 10% waste. Buy every box from one lot number and keep one spare
Boxes needed: 7 boxes; 140 sq ft purchased
Underlayment: 2 rolls; 100 sq ft per roll, covering 120 sq ft; over concrete pick a roll with a vapor barrier or add 6 mil poly under it
Quarter round or trim: 41 ft; 44 ft perimeter minus 3 ft for 1 doorway. Buy 6 pieces of 8 ft.

Laminate Flooring formula

Floor area (sq ft) = Length (ft) x Width (ft) + closets and hallways
Boxes = Floor area x (1 + waste %) / coverage per box, rounded up
Underlayment rolls = Floor area / 100 sq ft per roll, rounded up
Trim (ft) = 2 x (Length + Width) - 3 ft x doorways

Worked example

A 14 x 16 ft living room with two doorways: 14 x 16 = 224 sq ft. Add 10% waste for 246.4 sq ft. With boxes that cover 22.5 sq ft, 246.4 / 22.5 = 10.95, so buy 11 boxes (247.5 sq ft).

Underlayment: 224 / 100 = 2.24, so buy 3 rolls. Trim: the perimeter is 2 x (14 + 16) = 60 ft, minus 6 ft for the two doorways = 54 ft of quarter round, which is 7 pieces of 8 ft.

Quick reference

Laminate needed for common rooms (10% waste, 20 sq ft boxes, one doorway)
Room size	With 10% waste	Boxes	Underlayment rolls	Trim
10 x 10 ft	110 sq ft	6	1	37 ft
10 x 12 ft	132 sq ft	7	2	41 ft
12 x 12 ft	158 sq ft	8	2	45 ft
12 x 15 ft	198 sq ft	10	2	51 ft
15 x 20 ft	330 sq ft	17	3	67 ft
20 x 20 ft	440 sq ft	22	4	77 ft

How to calculate laminate flooring

Measure the room at its longest and widest points and multiply for square feet. Add closets and any hallway you will run the same floor into. Waste is the cut-off at the end of every row, the pieces under about 12 inches that should not start a row, and the cuts around jambs and closets: 10 percent for a rectangle, 15 for diagonal or L-shaped rooms. Divide by the coverage printed on the box. Round up, buy every box from one lot number, and keep one spare box for repairs.

Underlayment goes over the floor area only, so do not add waste to it. Planks with an attached pad get no foam roll under them; doubling pads voids the warranty and makes the joints spongy. Over a concrete slab you still need 6 mil polyethylene, seams taped and run up the wall behind the base, unless the pad has a vapor barrier built in. Test the slab first. Most makers want under 3 lb per 1,000 sq ft per 24 hours on a calcium chloride test, or 75 to 80 percent RH by ASTM F2170. Over a wood subfloor skip the poly; it traps moisture in the plywood. The subfloor has to be flat to 3/16 inch in 10 feet. Fill dips with floor patch, sand or grind high spots, and screw down any squeaks before the pad goes down.

Expansion gaps, trim and acclimation

Laminate is a floating floor and moves with humidity. Leave a 1/4 to 3/8 inch gap at every wall, cabinet, pipe and door jamb. Undercut the jambs with a jamb saw so the plank slides under instead of being scribed around. Cabinets and islands go in before the floor, and the floor stops short of them with the same gap. Quarter round or base shoe nailed to the baseboard, never to the floor, hides the gap. The trim length is the room perimeter minus the doorways, where a transition goes instead: T-molding between two floors of the same height, a reducer down to vinyl or tile, an end cap at an exterior door. Transitions are sold by the brand in 72 or 94 inch pieces, typically $30 to $60 each in 2026. A run over 40 feet needs a T-molding in the field.

The AC rating is the wear test: AC3 for bedrooms and living rooms, AC4 for kitchens, entries and halls with dogs, AC5 for commercial. Thickness (7 to 12 mm) is stiffness and feel, not wear; a 12 mm AC3 still scratches sooner than an 8 mm AC4. Let the sealed boxes sit flat in the room for 48 hours with the HVAC running at normal living conditions, 60 to 80 F and 35 to 65 percent humidity. The planks then match the room before you click them together. Boxes stacked in a garage or an unheated house are not acclimated.

What this calculator leaves out

Transitions and stair nose, the 6 mil poly over concrete, floor patch or self-leveler, and jamb undercuts. Pulling and reinstalling the baseboard, or the quarter round that hides the gap if the base stays. Tearing out and disposing of the old floor, moving furniture, and the spare box. Trim is counted for a rectangle; a closet or alcove adds its own perimeter.

Mistakes that cost money

A subfloor more than 3/16 in out of flat over 10 ft flexes the click joints until they pop; straightedge it and patch or grind.
Foam pad under planks with an attached pad voids the warranty and makes the joints spongy; over concrete use 6 mil poly only.
Quarter round nailed into the floor, or planks pinned under an island or vanity, stop the floor moving and it buckles at the seams.
Runs over 30 to 40 ft with no T-molding buckle in humid months; every doorway gets a transition and the gap it covers.
Two production runs differ in shade and sometimes in the click profile; buy every box from one lot and keep one spare.
Boxes acclimated in the garage are not acclimated; 48 hours flat in the room with the HVAC running at living temperature.

Key facts

Laminate is rated AC1 to AC5 for wear; AC3 is the minimum for a busy home and AC4 suits kitchens, hallways and light commercial use.
Leave a 1/4 to 3/8 in expansion gap at every wall and fixed object; quarter round or base shoe covers the gap.
Let boxes acclimate flat in the room for at least 48 hours before installation.
A roll of foam underlayment typically covers 100 sq ft; laminate with an attached pad does not need a separate roll.
Common laminate thicknesses are 7 to 12 mm; a typical box covers 18 to 24 sq ft.

Frequently asked questions

How many boxes of laminate do I need for a 12x12 room?

A 12 by 12 room is 144 square feet. With 10% waste that is 158 square feet, which is 8 boxes at 20 square feet per box.

Do I need underlayment under laminate flooring?

Yes, unless the planks have an attached pad. Foam underlayment evens out small subfloor flaws and reduces noise. Over concrete you also need a vapor barrier, either built into the underlayment or a separate 6 mil sheet.

How big should the expansion gap be for laminate?

Leave 1/4 to 3/8 inch at all walls and fixed objects. Rooms longer than about 40 feet in either direction also need a transition strip in the field.

Can I lay laminate over my existing floor?

Over sheet vinyl, tile or wood that is well stuck down and flat to 3/16 in over 10 ft, yes; the pad or poly goes right over it. Not over carpet, carpet pad or cushioned vinyl, which flex and pop the joints. Check the height change at exterior doors and under the dishwasher, which a floor 1/2 in taller can trap in place.

Sources and references

Laminate flooring FAQs: subfloors, underlayment and vapor barriers (NALFA)
How to install laminate and vinyl flooring (Pergo)
ROBERTS Serenity foam underlayment, 100 sq ft roll (QEP (Roberts))

Next steps for this project

The usual order for a flooring & tile project. See all flooring & tile calculators.

Results are estimates based on standard formulas and typical product specifications. Confirm quantities with your supplier and local code before ordering.