How to use the flooring calculator
- Enter the room’s length and width, or its total area if the room is irregular (work that out with the square footage calculator).
- Choose the layout. The more cuts the pattern needs, the bigger the waste allowance.
- Enter the coverage per box from the packaging — it varies between products.
- Add a price per box to see the total cost.
The flooring formula
Area to buy = floor area × (1 + waste % ÷ 100) Boxes = area to buy ÷ coverage per box (rounded up)
Worked example (US)
A 15 × 12 ft living room is 180 ft². With 10% waste you need 198 ft². Boxes of laminate covering 20 ft² each: 198 ÷ 20 = 9.9, so buy 10 boxes (200 ft²).
Worked example (UK)
A 4 × 3.5 m room is 14 m². With 10% waste that is 15.4 m². Packs covering 2 m²: 15.4 ÷ 2 = 7.7, so buy 8 packs (16 m²).
Waste allowance by layout
| Layout | Typical waste |
|---|---|
| Straight lay, simple rectangular room | 5–10% |
| Straight lay, rooms with alcoves, hearths or many doorways | 10–12% |
| Diagonal | 15% |
| Herringbone or chevron | 15–20% |
Before you lay the floor
- Acclimatise wood and laminate in the room for the time the manufacturer recommends — often 48 hours.
- Underlay: many laminate and wood floors need it; buy the same area as the floor (without the waste allowance), unless your flooring has it pre-attached.
- Expansion gap: floating floors need a gap around the edges, hidden by skirting, baseboard or trim.
- Laying tiles instead? Use the tile calculator, which accounts for tile size and grout joints.
Frequently asked questions
How much extra flooring should I buy?
Buy about 10% extra for a standard straight-laid floor in a typical room. Use 5–7% for large, simple rectangles, and 15% or more for diagonal layouts, herringbone or chevron patterns, or rooms with lots of corners and doorways.
How do I work out how many boxes of flooring I need?
Multiply the room’s area by 1 plus the waste allowance (e.g. 1.10 for 10%), then divide by the coverage printed on one box and round up. For example, 180 ft² × 1.10 = 198 ft²; with 20 ft² boxes that is 9.9, so buy 10 boxes.
Should I include closets and alcoves?
Yes — measure every area that will get the new floor, including closets, alcoves and the space under appliances such as dishwashers if the floor will run beneath them.
Should I keep a spare box?
It is a good idea. Flooring ranges are discontinued and dye lots change, so a spare box makes it possible to replace a damaged plank years later with an exact match.
Does this work for carpet?
For carpet tiles, yes — enter the coverage per box. Broadloom carpet comes off fixed-width rolls (often 12 ft in the US and 4 m or 5 m in the UK), so the amount depends on seam layout; use the area here as a starting point and ask the fitter.