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Flooring Calculator

How many boxes of flooring to buy, with a waste factor chosen for your actual layout.

Enter your room dimensions to see how many boxes to buy.

Rooms

Material

This covers cuts at the walls and around obstacles, not spare stock.

Printed on the box — usually 18 to 24 sq ft.

Estimate. A real-world figure based on the assumptions listed below, which you can change.

How this calculator works

Add each room, apply a waste factor, divide by the coverage on the box, and round up. The arithmetic is simple; the waste factor is where the judgement lies.

Waste is not padding. It is the material genuinely consumed by cuts at the walls, at doorways and around obstacles, plus planks rejected for damage or colour. The right figure depends on the layout rather than the product: a square room laid straight needs about 5%, a typical room 10%, an irregular room or a diagonal pattern 15% to 20%.

Boxes are always rounded up, and it is worth buying the whole job in one order. Boxes from different production runs can differ slightly in shade, so a top-up box bought later may not match.

The formula

Exactly what happens to your numbers, step by step.

  1. Area and waste

    floor area = Σ (length × width) for each room
with waste = floor area × (1 + waste %)

  2. Boxes

    boxes = ⌈area with waste ÷ coverage per box⌉

A worked example

A 15 × 12 foot living room plus a 10 × 4 foot hall, straight lay, boxes covering 20 sq ft.

What you enter

Living room
15 ft × 12 ft = 180 sq ft
Hall
10 ft × 4 ft = 40 sq ft
Waste
10%
Coverage per box
20 sq ft

The working

Floor area
220 sq ft
With 10% waste
242 sq ft
Boxes
⌈242 ÷ 20⌉ = 13
Actually buying
260 sq ft

13 boxes — 260 square feet

40 square feet spare sounds generous, but a doorway threshold and a couple of bad planks eat into it fast. Keep whatever is left for future repairs.

Assumptions

Every result here rests on these. Change your inputs and the result changes with them.

  • Rooms are rectangular. Split an irregular space into rectangles and add them separately.
  • Coverage per box is as printed on the packaging.
  • The waste factor covers cuts and a few rejected planks, not a change of layout.

What this cannot tell you

  • Underlayment, transition strips, trim and adhesive are not included.
  • It does not model plank direction or pattern layout, which affect how much is actually wasted.
  • Stairs need a different calculation entirely — count treads and risers individually.

Questions people ask

How much extra flooring should I buy?

Ten percent for a typical straight-laid room, 15% for irregular rooms or many cuts, and up to 20% for diagonal or herringbone patterns. Five percent is only enough for a simple square room.

Why should I buy it all at once?

Because production runs vary slightly in shade and texture. A box bought three months later may be visibly different, and there is no way to fix that once it is installed.

Should I keep the leftovers?

Yes. A spare box from the same run is the only reliable way to repair damage later. Store it flat and somewhere dry.

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Sources and review

This calculator uses standard arithmetic with no external rules or published rates, so there is nothing to cite beyond the formulas shown above.

Methodology version 1.0.0 · Last reviewed