METHOD / 04
How the flooring estimate works
Three separate calculations that happen to share one room measurement. Treating them as one number is how people end up with enough flooring and not enough of everything else.
Formula
packs = ceil(length × width × (1 + waste) ÷ pack coverage) · underlay rolls = ceil(floor area ÷ roll coverage) · skirting = ceil((perimeter − doorways) ÷ piece length)
Worked example
A 5 × 4 m room is 20 m². With 10% waste that is 22 m², and at 2.2 m² per pack you need 10 packs — exactly 22 m², with nothing spare, so an eleventh pack is worth considering. Underlay is sized on the bare 20 m², so two 15 m² rolls. Skirting: the perimeter is 18 m, one 80 cm doorway leaves 17.2 m, and at 2.4 m per length that is 8 lengths.
Common mistakes
- Sizing underlay on the flooring figure. Underlay is rolled out and cut to fit, so its offcuts stay usable and it does not need the plank waste allowance.
- Using 10% waste for a diagonal or herringbone layout. Those need 15% or more, because every perimeter piece is an angled cut that pairs with nothing.
- Forgetting that packs are sold whole. A result of 10.1 packs costs the same as 11.
- Skipping the expansion gap. It does not change the quantity — the planks still cover the whole floor — but leaving it out will buckle the floor in summer.
- Ordering skirting without counting internal corners. Each mitre eats part of a length, which is why the calculation rounds up per piece.
- Buying across two deliveries. Wood and laminate shade varies by batch, and a plank from the second order will show.
FAQ
Questions
How much waste should I allow?
8% for a straight lay in a square room, 10% once there are several doorways or an irregular shape, and 15% or more for a diagonal or herringbone pattern. Waste follows the number of cuts, which follows the perimeter and the pattern — not the size of the room.
Do I need underlay if the planks already have it attached?
Usually not a second acoustic layer, but you may still need a damp-proof membrane over concrete. Check what the attached backing actually provides; the two jobs are separate and only one of them is normally built in.
Should I deduct doorways from the skirting?
Yes, and this calculator does. A doorway carries no skirting across it, so its width comes out of the run. It does not come out of the floor area, though — you still floor the threshold.
Why does the result show the purchased area?
So you can see how much spare you are actually buying. When the purchased figure barely exceeds the required one, you have no margin for a mis-cut, and one more pack is cheap insurance compared with a second delivery from a different batch.
Estimates for planning a purchase, based on a rectangular room. Measure irregular rooms in sections and add the results. Confirm quantities against the product datasheet and, for a large or expensive floor, with your supplier before ordering.
About this material
Laminate and vinyl flooringAC wear classes, thickness, click systems and the underlay nobody budgets for.