Wallpaper Calculator

How to use the wallpaper calculator

Measure the room’s length, width, and wall height in feet, and count the doors and full-size windows. The calculator works out your wall area using the standard takeoff deductions — 21 sq ft per door, 15 per window — and converts it to rolls using realistic usable yields, not the optimistic gross square footage printed on the label.

The pattern-repeat setting is the one wallpaper newcomers miss, and it’s the difference between finishing the room and a panicked reorder. A repeat is the vertical distance before the design repeats itself; every strip must be cut so the pattern aligns with its neighbor ("drop matching"), and the offcut above and below each match is pure waste. No repeat or a random match keeps about 25 usable sq ft per single roll; repeats up to 12 inches drop that to roughly 22; big repeats over 12 inches — common on florals and damasks — leave only about 18. Check the repeat measurement on the product page; it’s always listed.

US wallpaper has a pricing quirk worth knowing before checkout: it’s usually PRICED per single roll but SOLD as double rolls — one physical bolt holding two single rolls of material. This calculator defaults to double rolls because that’s the unit that arrives at your door; flip the Advanced setting if a retailer genuinely sells singles. When comparing prices, double the per-single-roll price to get the real cost of the bolt.

Don’t deduct more than the standard door and window values, even when a wall has a big opening. Strips still have to be cut full-length and pattern-matched around every opening — the paper "saved" by a window mostly leaves as matching offcuts. The standard deductions already account for the realistic savings; over-deducting is the classic way to come up one strip short.

Buy every roll at once and check that all the batch (lot) numbers match — wallpaper printed in different runs shifts color enough to show as a seam-to-seam difference on the wall. Keep the leftovers and note the batch number somewhere safe: future repairs only match if they come from your run.

The formula

Wall area with standard deductions, divided by the USABLE yield of the roll format and pattern repeat you chose:

wall area = 2 × (length + width) × height − (doors × 21) − (windows × 15)
usable yield per single roll = 25 sq ft (no repeat) · 22 (≤12 in) · 18 (>12 in)
double-roll yield = single-roll yield × 2
rolls = wall area ÷ yield, rounded UP to a whole roll

Worked example with the defaults: a 12 × 10 ft room with 8 ft walls has 2 × 22 × 8 = 352 sq ft gross; one door (−21) and two windows (−30) leave 301 sq ft. With no pattern repeat and double rolls (50 usable sq ft each), 301 ÷ 50 = 6.02 — buy 7 double rolls. The same room in a large-repeat paper (36 usable per double roll) needs 9.

Rolls always round up: an 0.02-roll overage is still a full extra bolt, and that spare is your repair stock from the matching batch.

Frequently asked questions

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