How many packs of flooring do I need?

Work out the floor area in square metres, add an allowance for cuts, divide by the area one pack covers and round up to the next whole pack. A 4.2 m × 3.6 m room is 15.12 m², 16.632 m² with 10% extra, and needs 10 packs that each cover 1.84 m².

The four steps

1. Floor area = length × width, in metres. For an L-shaped or awkward room, split the floor into rectangles and add them.
2. Area to buy for = floor area × 1.1, for 10% extra.
3. Packs = area to buy for ÷ the coverage of one pack.
4. Round up to a whole pack, always, even when the answer is only just over a whole number.

Work with the unrounded figures and round once, at the end.

Where the pack coverage comes from

It is printed on the pack, in m² per pack. It changes from one product to the next, and even between board sizes in the same range, so take it from the pack you are buying. BuildBatch starts with 2 m² as a labelled example and asks you to replace it with the figure off your pack.

The 10% is a starting figure, not a standard. A diagonal or herringbone lay, a patterned board or an awkward room needs more; the wastage allowance guide says when.

Worked example

A room 4.2 m × 3.6 m, packs covering 1.84 m², 10% extra.

• Floor area: 4.2 × 3.6 = 15.12 m²
• Plus 10%: 15.12 × 1.1 = 16.632 m²
• Packs: 16.632 ÷ 1.84 = 9.04
• Rounded up: 10 packs, covering 10 × 1.84 = 18.4 m²
• Left over: 18.4 − 16.632 = about 1.77 m²

Nine packs would cover 16.56 m², about 0.07 m² short of the 16.632 m² to buy for. It is a small gap, but it is a gap, so the answer is 10.

A quick table

At 10% extra:

Floor	To buy for	Packs of 1.84 m²	Packs of 2 m²
3 m × 3 m = 9 m²	9.9 m²	6	5
4 m × 3 m = 12 m²	13.2 m²	8	7
4.2 m × 3.6 m = 15.12 m²	16.632 m²	10	9
5 m × 4 m = 20 m²	22 m²	12	11
6 m × 4.5 m = 27 m²	29.7 m²	17	15

Two things stand out. The pack size changes the count, by one pack in most rows and by two in the largest. And the 5 m × 4 m room in 2 m² packs comes to exactly 11: a whole-number answer does not buy an extra pack, because the 10% is already in it.

Two pack sizes: the combination matters

When a floor is sold in more than one pack size, the question is not only how many, but how many of each.

Say a floor came in packs of 1.84 m² and half packs of 0.92 m², and you need 16.632 m²:

Combination	Covers	Left over
10 × 1.84 m²	18.4 m²	about 1.77 m²
9 × 1.84 m² + 1 × 0.92 m²	17.48 m²	about 0.85 m²
9 × 1.84 m²	16.56 m²	about 0.07 m² short

The second line covers the floor with 0.92 m² less left over. Whether it also costs less depends on the prices of the two sizes, which only the shop can tell you.

BuildBatch compares only the sizes and prices you enter. With a price for every size, it picks the lowest total cost; with a price missing, the least left over. It shows the fewest-packs combination beside the answer whenever that is different.

Before you buy

• Buy all the packs at once, and where the packs show a batch or lot number, check that they match: the colour can vary from one batch to the next.
• Keep a board or two back after laying, for a repair later.
• The underlay, any membrane, the beading and the door bars are separate lines. See underlay and damp-proof membranes and measuring for skirting, beading and scotia.

Do it with BuildBatch

Open the Room Refresh Batch with flooring chosen, type the room and enter the coverage from your pack. Use “Add another pack size” for a second size, with prices if you have them, and it works out the combination and shows its working.

What this guide does not cover

Carpet and sheet vinyl, which are sold by roll width and need a different sum. Tiles laid to a set pattern. Stairs. Whether the floor suits the room, the subfloor or underfloor heating: the flooring’s instructions decide, so check first.

Related guides

• Measuring for laminate flooring
• Wastage allowance explained: why 10%, and when to allow more
• Underlay and damp-proof membranes: what to check first