Wallpaper calculator: how many rolls of wallpaper you need

How many rolls of wallpaper do I need?

This wallpaper calculator works the way paperhangers do: it counts strips, the lengths cut from the roll for the full wall height. Enter the room, the openings, the roll size and the pattern match to get the Rolls to buy, spares included, a step-by-step calculation and a diagram of the roll cut into strips. Imperial units are the default; switch to metric for rolls labelled in meters.

Measuring your room

1. Under How to enter the walls, pick Rectangular room (length × width), Wall by wall (accent wall, L-shaped room) or Perimeter already measured.
2. Measure along the baseboards, then the Ceiling height in a few places; keep the largest.
3. Add doors and windows, then the Roll size and Pattern match.
4. Copy link keeps the calculation for the store.

The strip method, worked through

A 12 × 10 ft bedroom, 8 ft ceiling, a 32 × 80 in door, a 36 × 48 in window, 27 in × 27 ft double rolls, no matching, 4 in trim.

• Strip length: 96 + 4 = 100 in.
• Strips per roll: 324 in ÷ 100 in = 3.24, so 3 whole strips and 24 in of waste.
• Perimeter: 2 × (12 + 10) = 44 ft, or 528 in. Strips: 528 ÷ 27 = 19.56, rounded up to 20.
• Rolls: 20 ÷ 3 = 6.67, so 7, or 8 with the spare.

Straight match and drop match

With a Straight match, the design lines up at the same height on every strip, so each strip is lengthened to the next multiple of the repeat printed on the label. With a 24 in repeat, 100 in becomes 5 × 24 = 120 in. A 27 ft roll now gives only 2 strips (324 ÷ 120 = 2.7), and the same 20 strips need 10 rolls instead of 7.

With a Drop match (half drop), every other strip starts half a repeat lower, so the calculator adds half a repeat to each strip: 132 in here.

Subtracting doors and windows, or not

You still paper above a door and below a window, so an opening only saves whole strips. The rule: opening area ÷ (roll width × wall height), whole number only. The door is 2,560 sq in against 27 × 96 = 2,592 sq in for a full strip: no strip saved, nor for the window. A 20.5 in roll would save 1 strip. Many decorators ignore small openings: tick Don't subtract small openings and set the threshold (10 sq ft by default).

Why the square-footage method comes up short

By area, the room is 352 − 17.8 − 12 = 322.2 sq ft. Each roll holds 60.75 sq ft, so 322.2 ÷ 60.75 = 5.30, or 6 rolls: one fewer than the 7 you really need, and four fewer with the 24 in repeat. It assumes every inch of the roll is used, yet each roll here leaves 24 in of waste and a match lengthens every strip.

Batch numbers, roll sizes, paste and tools

Common practice is one extra roll (Spare rolls) for a bad cut or a later repair. Buy everything at once, with the same batch number on every roll: two batches can differ slightly in shade.

US double rolls are typically 20.5 in × 33 ft or 27 in × 27 ft; European rolls are 0.53 × 10.05 m, wide non-woven ones 0.70 m. The paste figure is a rough estimate: check the coverage on the packaging (pre-pasted paper needs only water). Tools: tape measure, level, utility knife, straightedge, smoothing brush, sponge.

Frequently asked questions

How many rolls for a 12 × 12 ft room?

With 8 ft walls and 20.5 in × 33 ft rolls: 576 in ÷ 20.5 = 28.1, so 29 strips of 100 in, 3 per roll: 10 rolls before openings.

Is a single roll half a double roll?

Yes. Many US papers are priced per single roll but sold in double rolls: enter the length of the roll you'll actually unpack.

Why add a trim allowance?

Ceilings and floors are rarely straight; you trim top and bottom. Change it in Trim allowance per strip.

How is the ceiling handled?

Tick Paper the ceiling too: strips run along the longer side. For a 12 × 10 ft ceiling with 27 ft rolls, strips are 148 in, 2 per roll, 5 strips, so 3 extra rolls.