Flooring Calculator
Find how many boxes of laminate, vinyl plank or engineered wood, or how much carpet, to buy for your rooms. Advanced adds more rooms, waste by pattern, plank size, cost, underlay and skirting.
For an L-shaped room, add it as two rectangles. Take away things you won't floor under, like a kitchen island or fitted units.
Typical guidelines: straight lay about 5–10%, diagonal or herringbone about 15%. Add more for small rooms with many cuts.
Worked out round the edge of each room you add, less the doorways. For an L-shape made of two rectangles, leave out the edge where they join (counted twice).
How your flooring is worked out
Floor area, plus extra for cuts, divided by what one box covers and rounded up. Carpet is cut in strips from the roll.
- 1
Floor area
12 ft × 10 ft= 120 sq ft
- 2
Add the waste
120 × 1.10(10% extra)= 132 sq ft
- 3
Count the boxes
132 ÷ 20= 6.60, round up= 7 boxes
- 4
What you buy
7 × 20 = 140 sq ft8 sq ft left over= 7 boxes
Read more: the formula, worked examples, waste, carpet rolls and expansion gaps
Laminate, vinyl plank and engineered wood are sold by the box. Work out the floor area, add extra for cuts and waste, divide by the area one box covers and round up to whole boxes. Carpet is different: it comes off a roll of a fixed width, so you buy a length of the roll, and the width you can't use is offcut.
The formula
floor area = length × width for each room, added up, minus areas you take away
area with waste = floor area × (1 + waste % ÷ 100)
boxes = area with waste ÷ area one box covers, rounded up
one box covers = plank length × plank width × planks per box (if the box only lists planks)
left over = boxes × area one box covers − area with waste
carpet strips = room width across the roll ÷ roll width, rounded up; seams = strips − 1
carpet length = strips × (room length along the roll + trim)
carpet to buy = carpet length × roll width
underlay rolls = floor area ÷ area one roll covers, rounded up
skirting = 2 × (length + width) for each room − doorways − shared edges
Worked example
A room 12 ft long and 10 ft wide is 12 × 10 = 120 sq ft. Laying laminate straight, add 10%: 120 × 1.10 = 132 sq ft. If one box covers 20 sq ft, that is 132 ÷ 20 = 6.6, rounded up to 7 boxes. Seven boxes cover 7 × 20 = 140 sq ft, so 8 sq ft is left over after the waste allowance (20 sq ft more than the bare floor). At $40 a box the flooring costs 7 × 40 = $280.
Skirting for the same room: the edge is 2 × (12 + 10) = 44 ft. Take off one 3 ft doorway: 44 − 3 = 41 ft. With 10% for cuts that is 45.1 ft, so in 8 ft lengths you buy 45.1 ÷ 8 = 5.64, rounded up to 6 lengths.
Carpet for the same room from a 12 ft roll: the 12 ft side fits across the roll in one strip, so there are no seams. The strip runs the 10 ft way, plus 6 in for trimming: 10.5 ft of roll. That is 10.5 × 12 = 126 sq ft, or 126 ÷ 9 = 14 sq yd; at $30 a sq yd, $420.
In metric: a 5 × 4 m room is 20 m², 22 m² with 10% extra. Planks of 1285 × 192 mm cover 1.285 × 0.192 = 0.24672 m² each; 8 to a box is 1.97376 m² a box. 22 ÷ 1.97376 = 11.15, so 12 boxes (96 planks; 22 ÷ 0.24672 = 89.17, so 90 are needed). A 5 × 6 m room with a 4 m carpet roll needs 2 strips 5 m long either way across the 6 m side: 10 m of roll, 40 m² for a 30 m² floor, with 1 seam.
Waste by laying pattern
| Pattern | Typical extra | Why |
|---|---|---|
| Straight (along the room) | 5–10% | Cuts at the row ends and the last row |
| Diagonal (45°) | about 15% | Every edge plank is cut at an angle |
| Herringbone / chevron | about 15% | Many short angled cuts round the edge |
These are typical guidelines, not fixed rules. Add a few percent more for small rooms, rooms with many corners or doorways, and if you're new to fitting. Keep a spare box from the same batch for repairs.
Carpet rolls
- Common widths are 4 m and 5 m in the UK, Europe and much of the world, and 12 ft and 15 ft in the US. Some ranges also come in 3.66 m (12 ft) or 2 m.
- Carpet is sold by the length cut from the roll, priced per m², sq yd, or linear m or ft. You pay for the full width of every strip, even the part that is trimmed off.
- "Least carpet" tries the strips both ways and picks the shorter length, then the one with fewer seams. Fitters may choose differently to keep seams out of walkways or to run the pile towards the light.
- Patterned carpet needs each strip to start at the same point in the pattern, so each strip is rounded up to whole pattern repeats.
- Wide offcuts can sometimes fill a small area such as a cupboard; this calculator doesn't count on that.
Expansion gap
| Floor | Typical gap round the walls |
|---|---|
| Laminate | 8–10 mm (about 3/8 in) |
| Vinyl click plank | 5–8 mm (about 1/4 in) |
| Engineered wood | 10–15 mm (about 1/2 in) |
| Carpet | None: held by gripper strips at the wall |
Floating floors grow and shrink with heat and damp, so leave the gap round every wall, pipe and door frame. The skirting or a trim covers it, and it doesn't change how much flooring you buy. Very large or long rooms may need a joint in the floor; check the maker's limit.
Waste allowances, roll widths and expansion gaps are typical figures, not fixed rules; follow the maker's instructions for your product. Box coverage varies a lot between ranges, so use the figure printed on your box. Checked on 13 October 2026.
Common questions
How do I work out how much flooring I need?
Measure each room's length and width and multiply them to get the floor area. Add the areas together, take away anything you won't cover, then add about 10% for cuts and waste. Divide by the area one box covers and round up. A 12 × 10 ft room is 120 sq ft, 132 sq ft with 10%, so with boxes of 20 sq ft you buy 7 boxes.
How much extra flooring should I buy for waste?
As a typical guide, 5–10% for planks laid straight and about 15% for diagonal or herringbone. Add a little more for small rooms, rooms with many corners and if you're new to fitting. Keep a spare box for later repairs.
How many boxes of laminate do I need?
Divide the area to buy, including waste, by the area per box printed on the box, and round up. For 22 m² and boxes of 1.97 m² that is 11.15, so 12 boxes.
How much carpet do I need for a room?
Carpet comes off a roll of a set width, usually 4 or 5 m, or 12 or 15 ft. Count how many strips of that width cover the room, multiply by the room's length plus a little for trimming, and that is the length to cut. A 12 × 10 ft room with a 12 ft roll needs one strip 10.5 ft long: 126 sq ft, or 14 sq yd.
How much underlay do I need?
Underlay covers the floor edge to edge with no waste for pattern, so divide the floor area by what one roll covers and round up. A 15.5 m² floor with 10 m² rolls needs 2 rolls.
What expansion gap does laminate need?
Typically 8–10 mm (about 3/8 in) round every wall and fixed object; vinyl click planks often 5–8 mm and engineered wood 10–15 mm. The skirting or trim hides the gap. Always follow the maker's instructions for your floor.
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