About Wallpaper Calculator (Rolls by Pattern Repeat)
The wallpaper calculator estimates how many rolls of wallpaper you need for a room. Enter the wall perimeter and wall height — the gross wall area is perimeter × height — and deduct the square footage of doors, windows, and built-ins. The net area is then divided by the usable coverage of a single roll, which shrinks as the pattern repeat grows: the wallcovering trade's estimating table gives 25 ft² per single roll for paper with no repeat or a repeat up to 6 inches, 22 ft² for a 7–12 inch repeat, 20 ft² for 13–18 inches, and 18 ft² for 19–23 inches.
The pattern repeat reduces each roll's usable coverage because every strip must be cut so the motif lines up with the strip beside it — the offcut above the match point is waste, and the bigger the repeat, the bigger the average offcut. The calculator rounds the single-roll count up to whole rolls, converts it to double rolls (two continuous singles), and shows the purchase quantity in whichever format you toggle — most wallpaper sold in the US is priced and packaged as double rolls even when the pattern book quotes single-roll coverage.
How It Works
- Enter the perimeter of the walls to be papered (add up the wall lengths) and the wall height; the gross area is perimeter × height.
- Enter the total openings — doors, windows, a fireplace, built-ins — in square feet; they are deducted from the gross area. If the openings meet or exceed the wall area, the calculator flags it instead of returning a nonsense count.
- Pick the pattern-repeat range printed on the label or in the pattern book. The repeat sets the usable coverage of each single roll from the verified trade table: 25 / 22 / 20 / 18 ft² for no-or-small (0–6″), 7–12″, 13–18″, and 19–23″ repeats.
- Single rolls = net area ÷ usable coverage, rounded up to a whole roll; double rolls = single rolls ÷ 2, rounded up — an odd single-roll count means the last double roll includes a spare single.
- Toggle the purchase format to match how your paper sells (double rolls for most US brands, single rolls for some boutique and European lines) and read the rolls to buy, the coverage purchased, and the leftover.
Worked Example
A room with 40 ft of papered perimeter and 8 ft walls has a gross area of 40 × 8 = 320 ft². A door and two windows total 40 ft² of openings, leaving 280 ft² to paper. The chosen paper has a 15-inch repeat, which falls in the 13–18″ bucket at 20 ft² of usable coverage per single roll, so the job needs 280 ÷ 20 = 14 single rolls exactly. Fourteen singles are 7 double rolls — the format most US wallpaper actually sells in — and the purchase covers 14 × 20 = 280 ft² with nothing to spare, so many hangers would add one extra double roll for repairs and matching errors.
Formulas
- Net wall area
A_net = P × H − A_openings- Single rolls
n_single = ceil( A_net ÷ U_repeat )- Double rolls (US purchase format)
n_double = ceil( n_single ÷ 2 )
Standards & References
- Wallcovering-trade estimating practice — usable-yield table (25/22/20/18 ft² per single roll by pattern repeat) verified against Hirshfield's wallcovering "How to Measure" guide; ROMAN Products' pattern-repeat guide corroborates (no repeat 25 ft², under 12″ 22 ft², over 12″ 18 ft²)
- US roll convention — the standard single roll is ~28 ft² gross (Euro/metric size, ~20.5″ × 16.5 ft) and nearly all US wallpaper is packaged and sold as double rolls
Frequently Asked Questions
Why does the pattern repeat change how many rolls I need?
Every strip has to be hung so the motif lines up with the strip next to it. To find the match, you slide the strip up to a full repeat and cut off the excess — that offcut is pure waste, and on average it grows with the repeat length. The trade estimating table bakes that waste in: a single roll yields about 25 ft² with no repeat or one up to 6 inches, 22 ft² at 7–12 inches, 20 ft² at 13–18 inches, and 18 ft² at 19–23 inches.
What is the difference between a single roll and a double roll?
A double roll is one continuous bolt equal to two single rolls — same width, twice the length. US pattern books traditionally quote coverage per single roll, but nearly everything sold in the US ships as double rolls, so a 14-single-roll estimate means buying 7 double rolls. The calculator shows both counts and lets you toggle the purchase format.
Why does an odd single-roll count cost me a whole extra single?
Because double rolls are indivisible: if the math says 15 single rolls, you must buy 8 double rolls — 16 single-roll equivalents — and the spare single is leftover. That is not wasted money in practice; keeping an uncut roll from the same dye lot is the standard insurance for future repairs and replacement strips.
Do European or metric rolls change the numbers?
The usable-yield table here is for the standard roll sold in the US, which is itself the Euro/metric size — about 20.5 inches wide by 16.5 feet per single roll (~28 ft² gross). Wider commercial goods (54″ contract vinyl), grasscloth in 36″ widths, and some UK rolls quoted at 33 ft × 20.5″ have different dimensions and are outside this calculator's scope — estimate those by counting strips per roll at your wall height and repeat.
Should I buy an extra roll beyond the estimate?
Most professional hangers say yes: one extra double roll covers cutting mistakes, damaged strips, tricky corners, and future repairs from the same dye lot — a later reorder is very likely to be a slightly different shade. It matters most when the estimate lands with little leftover, like the worked example that comes out exactly even at 7 double rolls.
What if my repeat is bigger than 23 inches, or the paper is a drop match?
The verified trade table tops out at a 19–23 inch bucket. For oversized repeats and half-drop matches — where alternate strips shift by half a repeat — waste can be higher than any table value, so estimate by strips: usable strip length is your wall height rounded up to a whole number of repeats, and each roll yields floor(roll length ÷ strip length) strips. When in doubt, order per your supplier's guidance for that specific pattern.