How the flooring calculator works
Click-together floors are sold in sealed packs that cover a fixed area, so the calculation has three steps: measure the floor, add a margin for the offcuts that cannot be reused, then divide by the pack coverage and round up. The margin grows with the pattern because angled cuts at the walls produce more unusable pieces.
Packs = room length × room width × (1 + waste %) ÷ coverage per pack, rounded upUnderlay is laid edge to edge under the whole floor, so its quantity is based on the bare room area plus 5% for trimming at the walls and around door frames.
Worked example
A living room of 5 m × 4 m has 20 m² of floor. Laminate laid straight needs 7% extra, so 20 × 1.07 = 21.4 m². The chosen laminate comes in packs of 2.22 m², and 21.4 ÷ 2.22 = 9.64, so you buy 10 packs holding 22.2 m². The foam underlay comes in 15 m² rolls: 20 × 1.05 = 21 m², which means 2 rolls. In imperial units the same logic gives a 16 × 13 ft room of 208 ft², 222.6 ft² with the margin, and 10 cartons of 23.9 ft².
Typical pack sizes and expansion gaps
| Product | Usual pack coverage | Common board thickness | Gap at walls |
|---|---|---|---|
| Laminate | 1.8–2.5 m² (20–27 ft²) | 7–12 mm | 8–10 mm (3/8 in) |
| Engineered wood | 1.3–2.6 m² (14–28 ft²) | 10–15 mm | 10–15 mm (1/2 in) |
| Rigid core vinyl plank | 1.5–2.2 m² (16–24 ft²) | 4–8 mm | 5–8 mm (1/4 in) |
| Solid hardwood strip | 1.5–2.0 m² (16–22 ft²) | 18–20 mm (3/4 in) | 15 mm (5/8 in) |
The gap lets the floor expand with humidity. Skirting boards or quarter-round beading hide it, so it never shows once the room is finished. Always follow the gap stated in the fitting instructions of the product you buy.
Choosing the waste percentage
Seven percent suits a normal rectangular room with boards parallel to the longest wall. Go higher for narrow corridors, rooms with bay windows or many door openings, and for long boards over 1.8 m, because the offcut from the end of each row is more often too short to start the next one. Herringbone and chevron parquet is sold as left and right blocks, and every perimeter piece is mitred, so 15% is a realistic minimum.
Mistakes to avoid
- Skipping acclimatisation. Leave unopened packs flat in the room for 48 hours so the boards reach room temperature and humidity before fitting.
- No moisture barrier on concrete. On a slab or screed, lay a 0.2 mm (about 8 mil; US installers often specify 6 mil, 0.15 mm) polyethylene film under the underlay unless the underlay already includes one.
- Stacking joints. Stagger the end joints by at least 30 cm (12 in) between neighbouring rows, and avoid a last row narrower than a third of a board by trimming the first row too.
- Double underlay. Vinyl and laminate with a pre-attached pad must not go over a second soft underlay, which strains the click joints.
Frequently asked questions
How many boxes of laminate do I need for a 12x12 room?
A 12 × 12 ft room is 144 ft². With 7% waste you need about 154 ft², so 7 cartons of 23.9 ft² (167 ft²).
How much extra flooring should I buy?
Plan 5–10% for a straight layout, 10–15% for a diagonal layout and at least 15% for herringbone or chevron. Keep one unopened pack for future repairs.
How many square metres are in a pack of laminate?
Most laminate packs cover between 1.8 and 2.5 m², often 2.22 m² or 2.49 m². The exact figure is printed on the end label of every pack.
Do I need underlay under vinyl plank flooring?
Many rigid core vinyl planks have a pad bonded underneath and need only a moisture film on concrete. Loose vinyl planks without a pad usually need a thin underlay of 1–2 mm specified by the maker.
How big should the expansion gap be for laminate?
Most makers ask for 8–10 mm (about 3/8 in) at every wall, pipe and door frame, and an extra expansion profile for runs longer than about 10–12 m.
Last reviewed: 2026-09-27 · How we calculate