How to use this calculator
- Measure the room's length and width at the widest points, or enter the area.
- Enter the coverage printed on one pack of your chosen flooring.
- Choose the layout — the spare fills in automatically.
- Add the underlay roll coverage if you need underlay.
The formula
Area with spare = floor area × (1 + spare %)
Packs = area with spare ÷ coverage per pack, rounded up
Underlay rolls = floor area ÷ coverage per roll, rounded up
Boards are cut at the end of every row, and the offcut can often start the next row, so straight layouts waste little — about 5–10 %. Diagonal and herringbone layouts cut far more, so 15 % is a safer figure.
Underlay is laid edge to edge without overlapping, so it doesn't need the same spare.
Worked example
A 5 m × 4 m room with 8% spare needs 21.6 m² of flooring.
With packs covering 2.22 m², that's 10 packs, which cover 22.2 m².
Underlay at 15 m² a roll: 2 rolls.
Tips before you buy
- Let the packs rest flat in the room for the time the maker recommends (often 48 hours) before fitting.
- Measure into door frames and alcoves — they add up.
- Buy one extra pack if the colour or pattern may be discontinued.
Frequently asked questions
›How much extra laminate should I buy?
Around 5–10 % for straight layouts and 15 % for diagonal or herringbone. Rooms with many corners, pipes or doorways need a little more.
›Do I include the expansion gap in the area?
No. Measure wall to wall; the small gap is covered by skirting and makes no real difference to the quantity.
›Can I return unopened packs?
Many shops accept unopened packs — check before you buy. Buying slightly more and returning a pack is better than running out mid-job.
Sources
- Formula: floor area × spare ÷ pack coverage. Waste allowances: common manufacturer and fitter guidance.
Formulas last reviewed: September 29, 2026. How we check our formulas