How this is calculated
Net wall area is perimeter × height minus door and window openings. Pattern repeats and trimming waste mean you never order the exact area divided by roll coverage.
Default usable coverage assumes a typical single roll after trim. Large repeats and drop matches need a higher waste percent — or the coverage number printed on your roll.
Formula & methodology
Net area = (2 × (L + W) × H) − openings. Adjusted = net × (1 + waste %). Rolls = ceil(adjusted ÷ coverage per roll).
Worked example
A 14 × 12 ft room, 8 ft ceilings, 1 door, 2 windows, 15% waste
- 1.Perimeter = 2 × (14 + 12) = 52 ft
- 2.Gross walls = 52 × 8 = 416 ft²
- 3.Openings ≈ 21 + 15 + 15 = 51 ft² → net ≈ 365 ft²
- 4.With 15% waste ≈ 420 ft² ÷ 27 ft²/roll ≈ 16 rolls
Frequently asked questions
How much pattern waste should I use?
Plain or random-match papers often work with about 10%. Straight-across or drop matches with a large repeat commonly need 15–20%. When in doubt, round up a roll.
Single roll vs double roll?
US stores often sell double rolls but quote coverage per single roll on the label. Enter the usable coverage for the unit you are buying, or convert doubles to singles consistently.
Should I wallpaper the ceiling?
This tool is for vertical walls. Ceiling area is length × width — run a separate takeoff if you are papering overhead.
Textured or feature wall only?
Measure only the walls you will cover. A single feature wall is one length × height, not the full room perimeter.
Paste and liner included?
No. Paste, liner paper, and sizing are separate. Budget them from the product instructions once you know roll count.
UK metric rolls?
Switch to metric and set coverage from the roll label (often around 5 m² usable before a heavy pattern match). Do not assume US single-roll coverage.
Last updated 2026-09-12. Formulas are planning methods — confirm with a supplier before you order.