Wallpaper Calculator — Rolls with Pattern Repeat
How many rolls to buy, worked out drop by drop with your paper’s repeat and match.
Walls to paper
One row per wall size: width, the height to paper (top of the skirting to the ceiling) and how many walls of that size.
Doors and windows optional
A door or window replaces the drops that fall wholly inside its width by short pieces above (and below) it. Openings narrower than a roll only reduce the paste.
The wallpaper
Paste and price optional
Cutting plan
Cut the longest pieces first; the short ones over doors and windows come from the ends of the rolls.
| Roll | Pieces to cut | Left over |
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Walls and paper
About the Wallpaper Calculator — Rolls with Pattern Repeat
Work out how many rolls of wallpaper a room needs the way a decorator does: drop by drop. Enter each wall, the doors and windows, the roll size and the paper’s pattern repeat and match from the label, and the calculator lists every piece to cut — full-height drops and the short pieces over doors and above and below windows — rounds each one for the pattern, and fits them onto rolls, longest first, so you see a cutting plan roll by roll and not just a total.
It starts from the European roll (0.53 m × 10.05 m) or the US roll (20.5 in × 33 ft, often sold as a "double roll"), or any size you type. It also gives the paste to mix from the coverage on your pack and the cost at your price per roll. Work in metres or in feet and inches; nothing you type leaves your device.
How to use it
- Choose metric or US units, then add a row for each wall size: the width, the height to paper (top of the skirting to the ceiling or picture rail) and how many walls of that size.
- Add the doors and windows: which wall they are in, their width and height and, for a window, the height of its bottom edge above the floor.
- Pick the roll size — European, US or another size from the label — and the pattern match. For a straight or offset (half-drop) match, type the pattern repeat printed on the label.
- Keep a trim allowance of about 10 cm (4 in) per piece for cutting at the ceiling and the skirting, and add any extra rolls you want for repairs.
- Optionally enter the paste coverage from the pack (m² per litre, ft² per US gallon, or the rolls one pack hangs) and the price per roll.
- Read the rolls to buy, then follow the cutting plan; copy the summary or download the cutting list as CSV.
Examples
Walls 2 × 4 m and 2 × 3 m, 2.4 m high · trim 10 cm · free match
28 drops of 2.5 m (8 per 4 m wall, 6 per 3 m wall) · 4 drops per 10.05 m roll → 7 rolls
Straight match, repeat 53 cm
Each drop rounds up to 5 repeats = 2.65 m · up to 53 cm lost finding the match on each roll leaves room for 3 drops → 10 rolls
Door in wall 1, window in wall 2
25 full drops + 5 short pieces (0.4 m above the door and the window, 1 m below the window) · the short pieces come from the end of roll 7 → 7 rolls
Trim 4 in · free match
28 drops of 8 ft 4 in · 3 per 33 ft roll → 10 rolls; with 2 in of trim four 8 ft 2 in drops fit a roll → 7 rolls
Room 4 × 3 m, 2.1 m high, trim 10 cm, 64 cm repeat
Straight match: 2.56 m per drop, 3 per roll → 10 rolls · offset (half-drop): 2.24 m per drop, 4 per roll → 7 rolls
How the rolls are worked out
- Drops: each wall needs ceil(wall width ÷ roll width) full-height strips. A door or window replaces the strips that fall wholly inside its width — floor(opening width ÷ roll width) of them — by short pieces: one above it and, for a window, one below it.
- Length of each piece: its height on the wall plus the trim allowance. With a straight match every piece must start on the same point of the pattern, so it uses that length rounded up to whole repeats: ceil(length ÷ repeat) × repeat. With an offset (half-drop) match neighbouring drops start half a repeat apart, so cut in turn from one roll each drop uses the shortest (k + ½) × repeat that holds it.
- Rolls: up to one repeat (half a repeat for a half-drop) can be lost at the start of every roll before the pattern lines up. The pieces are then fitted longest first, each onto the first roll with room left, and the last piece on a roll needs only its own length. That is the number of rolls; extra rolls are added on top.
- Paste: the net wall area (doors and windows taken off) for papers you paste on the wall, or the paper hung for papers pasted on the back, divided by the coverage on the pack.
Roll sizes
The European roll is 10.05 m long and 53 cm wide (5.33 m²): the nominal size that the European standard EN 233 sets for finished wallcoverings, within 1.5 % (Deutsches Tapeten-Institut). US wallcoverings are commonly 20.5 in wide and 33 ft long, about 56 ft², sold as a "double roll" or bolt (Brewster Home Fashions). Wider papers, murals, grasscloths and textiles come in other sizes — choose other size and type the width and length from the label, because the label is what counts.
Pattern repeat and match
- Free match (also called random match): stripes, textures and plains that line up anywhere. No pattern waste.
- Straight match: the design runs straight across, so every drop starts at the same point of the pattern. The waste per drop is the gap between the drop and the next whole repeat.
- Offset or half-drop match: the design on every other drop sits half a repeat lower. It is often said to waste more, and it often does, but not always — when the drop is just over a whole number of repeats, alternate drops nest into each other and it can waste less than a straight match (see the last example). Decorators also cut large half-drop patterns from two rolls at once, odd drops from one and even drops from the other; this calculator assumes the simpler one-roll order.
The repeat and the match symbol are printed on the roll label. Buy all rolls with the same batch number on the label — colour can differ slightly from batch to batch (Deutsches Tapeten-Institut).
Trim and paste
York Wallcoverings’ installation guide suggests about 4 in (10 cm) of extra length per strip — roughly 2 in at the ceiling and 2 in at the baseboard — which is the default here. Paste coverage varies a lot between pastes and papers, so the calculator only uses the figure from your pack: either an area per litre or gallon of mixed paste, or the number of rolls one packet hangs.
Limitations
- Rectangular walls only. Sloping ceilings, stairwells and dormers: split them into rectangles of their own height, and expect more offcuts.
- Pieces under windows are cut to the pattern from the roll like any other piece; in practice lining them up at the sill can take up to one more repeat each.
- It does not paper ceilings, and it assumes the paper is hung vertically from roll to roll in one direction (no railroading).
- It cannot read the label for you: the roll size, repeat and match come from the paper you choose. Paste coverage comes only from your pack.
Privacy
Everything happens in your browser. What you enter or open here is not uploaded or stored by MySmartCoPilot.
Frequently asked questions
How many rolls of wallpaper do I need for a 4 × 3 m room?
With walls 2.4 m high and a plain paper on 0.53 × 10.05 m rolls: 28 drops of 2.5 m (with 10 cm for trimming) and 4 drops per roll, so 7 rolls. A 53 cm straight-match pattern makes each drop 2.65 m, only 3 fit on a roll, and you need 10 rolls.
What is the difference between a straight match and a half-drop?
In a straight match the pattern lines up straight across the wall, so every drop starts at the same point of the pattern. In a half-drop (offset) match the pattern on every other drop sits half a repeat lower, so neighbouring drops start half a repeat apart on the roll. Both waste paper to line the pattern up; which wastes more depends on how the wall height compares with the repeat.
How do I find the pattern repeat?
It is on the roll label, usually with a symbol for the match — for example "repeat 64 cm, straight match". On a sample you can measure it as the distance from one point of the pattern to the same point further down.
Do doors and windows reduce the number of rolls?
Only when they are wider than a roll. A door 0.9 m wide on 53 cm paper replaces one full drop by a short piece above it, and those short pieces usually come from the ends of rolls you are using anyway. A narrow window saves no paper but still comes off the paste.
Should I buy an extra roll?
It is wise to keep one from the same batch for repairs and mistakes, because a roll bought later may come from a different batch and differ in colour. Add it under Extra rolls.
How much paste do I need?
Use the coverage on the pack: the calculator divides the area to paste by it (the wall for paste-the-wall papers, the back of the paper otherwise) or divides the rolls by the number one packet hangs.