How much flooring do I need? How to use the calculator
- 1Measure the room's length and width at the widest points, or enter the area.
- 2Take off any floor the flooring does not go under, such as fixed kitchen units.
- 3Enter the coverage printed on one pack of your chosen flooring.
- 4Choose the layout — the spare fills in automatically.
- 5Add the underlay roll coverage if you need underlay.
How to calculate flooring packs (formula)
- 01Floor to cover = floor area − area not covered
- 02Area with spare = floor to cover × (1 + spare %)
- 03Packs = area with spare ÷ coverage per pack, rounded up
- 04Underlay rolls = floor to cover × 1.05 ÷ 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 — but the edges are trimmed at the walls, so 5 % is added (retailers suggest 5–10 %).
Pack sizes differ a lot between products and makers, so the coverage box starts empty: a guessed figure could leave you several packs short.
Flooring calculation 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.
Do I lay flooring under kitchen units?
Usually not: floating floors such as laminate must not be trapped under fixed units, so fit them up to the plinth. Enter the floor under the units as the area not covered.
How do I work out sheet vinyl or lino?
Sheet flooring comes off a roll of fixed width (2, 3 or 4 m in the UK and Europe), so you buy a length of the full roll width. Use the carpet calculator, which chooses the direction that needs the least and shows any joins.
How many boxes of flooring do I need?
Room area plus spare, divided by what one box covers, rounded up. A 12 × 14 ft room is 168 ft²; with 10 % spare that is 184.8 ft², so boxes of 20 ft² give 184.8 ÷ 20 = 9.2 — buy 10 boxes.
How do I measure a room for vinyl or laminate flooring?
Measure the longest length and width wall to wall, into doorways the flooring will run through. Split an L-shaped room into rectangles and add them. Then add 5–10 % for a straight lay, more for diagonal or herringbone, and divide by the coverage on the box.
Sources
- Formula: floor area × spare ÷ pack coverage. Waste allowances: common manufacturer and fitter guidance.
- Underlay: a 5–10 % allowance is usually enough — Online Carpets
- Vinyl is sold in 2 m, 3 m or 4 m roll widths, cut to length — Online Carpets
Formulas last reviewed: September 30, 2026 ·How we check our formulas