Plan wallpaper strips around doors and windows
Openings do not remove strips in this calculator. Decide where a drop starts, then add a spare roll only when you mean to.
The wallpaper calculator counts full-height strips for all four walls of a rectangular room. A door or a window does not delete a strip, and a short piece above a door is not returned to the roll. If your hanger will reuse those shorts, this result can be higher than that method. The way to add paper for a difficult start is the spare-rolls field, not a longer wall.
The test room does not move when you add a door
“Try the test example” on the wallpaper calculator loads a synthetic free-match paper: width 0.53 m, length 10 m, total trim 0.1 m, roll-start allowance 0, spare rolls 0, owned rolls 0. The room is 4 m × 3 m × 2.5 m.
Length walls: ceil(4 ÷ 0.53) = 8, twice, so 16 strips.
Width walls: ceil(3 ÷ 0.53) = 6, twice, so 12 strips. Total = 28.
Cut length = 2.5 + 0.1 = 2.6 m. Strips per roll = floor(10 ÷ 2.6) = 3.
Base rolls = ceil(28 ÷ 3) = 10.
A door of 0.9 m × 2.1 m, or a window of 1.2 m × 1.0 m, changes none of those lines. Paint would deduct 0.9 × 2.1 = 1.89 m² from walls only. This model will not. Pattern, repeat and roll length are in the pattern and repeat guide. The contrast with paint openings is in deduct doors and windows.
The piece above the door is not a saved strip
On the test wall the clear height above a 2.1 m door is 2.5 − 2.1 = 0.4 m, before trim. The calculator still cuts 2.6 m drops. It will not slice one of those drops into a 0.4 m header and put the rest back on the roll. If the label’s method allows that header to come from an offcut, the 10-roll count can be conservative. This page does not turn that possibility into a lower number, because the tool will not either. Compare the assumptions before you buy fewer rolls than the estimate.
A window reveal you intend to paper is extra face the model ignores. If those reveals need their own short pieces and you will not use tails, that judgement is a spare roll, not a fifth wall typed into the room.
Where the first strip starts
Each wall is already rounded up to a full strip width. A 4 m wall at 0.53 m is 8 strips (4.24 m of paper width). Starting the first drop at a door jamb instead of the corner does not, by itself, add a ninth strip. It can force two partial widths, one at the jamb and one at the far corner, that do not share a piece. The model does not add a second partial for centring or for a seam you want just past the architrave. If that start really discards one extra full-height strip on that wall, account for it with spare rolls. Do not add the door width onto the wall length.
Wrong shortcut: type 4.9 m because the wall is 4 m and the door is 0.9 m.
Length walls become 2 × ceil(4.9 ÷ 0.53) = 2 × 10 = 20, not 16.
Width walls stay 12. Total strips = 32, not 28.
ceil(32 ÷ 3) = 11 base rolls. The extra roll came from the mistyped length.
The door opening is not 0.9 m of extra wall. Inflating both the length and the width, or inflating only one and then duplicating the room, stacks the same mistake. Measure the wall run that exists. Keep the opening out of the length fields.
The spare roll is the explicit extra
Same free-match test: 28 strips, 3 per roll, 10 base rolls.
Spare rolls 1 → need 11. With none owned, buy 11.
Spare rolls 1 and owned rolls 2 → buy 9.
A half roll is rejected. Spare rolls are a whole number, including 0 when you mean none.
Use that field for a deliberate extra: a centred pattern, a reveal, a start you expect to waste, or a roll you want unopened for shading. Do not also lengthen the room. That would count the opening twice, once as strips and once as spare. Owned stock is usable whole rolls of the same product, subtracted after spare rolls. The calculator does not check batch or shading.
Straight match can change the cut length and the strips per roll. The repeat guide shows a 0.64 m repeat and a 1 m start allowance moving this room from 10 rolls to 14, with no door involved. Openings do not replace that arithmetic. Set match, repeat, trim and start allowance first. Add spare rolls after the base count is one you can recompute.
What still stays outside the roll count
- Corners are not joints the tool can plan. A partial width wrapped around a corner is a hanger’s method, not a deducted strip.
- Offset, half-drop and murals are blocked. Do not approximate them by adding a door.
- Different wall heights on one product are rejected. A hall and a stair need separate entries. Mixed heights can be more conservative than one cutter’s plan.
- Price “per roll” must match the physical length you entered. A double roll typed as 10 m when the bolt is 5 m changes the yield. See the pattern guide before you halve a nickname.
Confirm physical width, physical length, match and an explicit start allowance, including 0. Read strips, cut length and strips per roll. Then set spare rolls to the extra you can explain, not to a remembered “one for the windows” unless that is the decision you mean. Plan the rolls from the roll in front of you, or return to the home page to switch material. The count is a disclosed full-strip model. It is not a site measure of your reveals.
Sources and scope
For definitions of wallpaper match, repeat and packaging, see Brewster's product properties and Graham & Brown's wallpaper FAQ. Product instructions take precedence over generic examples. Unit conversions use the exact international foot (0.3048 m) and US liquid gallon (3.785411784 L); see NIST conversion factors.