Wallpaper calculator: how many rolls do I need?

How do I measure my walls?

Measure each wall on its own and enter it as its own row. Take the width straight across, then the height you'll actually paper, which is usually from the top of the baseboard to the ceiling. Ceilings aren't always level, so measure the height at both ends and enter the taller one.

Don't subtract doors or windows from a wall's width. They have their own rows, and the section on doors and windows below explains why they don't cut the roll count.

You'll find the pattern repeat on the roll label or the product page. It's the distance down the paper before the design starts again. A plain paper or a random pattern has no repeat, so enter 0 or choose free match.

How does the calculator count rolls?

Wallpaper goes up in drops: one floor to ceiling strip each. So the calculator counts drops, not square feet.

For each wall it works out how many drops cover the width. Then it works out the cut length of each drop, which is your wall height plus enough extra to line the pattern up, plus a trim allowance. Finally it packs those drops onto rolls in order and counts the rolls.

Here's a worked example. One wall, 12 ft wide and 8 ft high. A 20.5 in by 11 yd roll, a 21 in pattern repeat, straight match, and our 4 in trim allowance.

• Each drop is cut to 8 ft 9 in: 8 ft 0 in of wall, 5 in to line up the repeat, and 4 in of trim.
• The wall takes 8 drops.
• Each roll holds 3 of those drops, so you buy 3 rolls.
• Your last roll has 186 in unused: enough for 1 more whole drop, plus 81 in of offcut.

The drops from every wall share the same rolls, so a half used roll carries over to the next wall. Two narrow walls, each 20 in wide and 8 ft high, take one roll between them on the default roll with no repeat. Not one roll each.

What does the match type cost you?

The match type changes the cut length, and sometimes the roll count.

• Free match: there's no pattern to line up. Each drop is the wall height plus trim.
• Straight match: every drop is rounded up to a whole number of repeats.
• Half drop: the pattern shifts by half a repeat on every other drop, so on each wall, drops can alternate between two lengths.
• Quarter drop: the pattern shifts by a quarter repeat each time, cycling through four positions.

The calculator prints the difference in rolls against free match on the same walls. Take a wall 10 ft wide and 8 ft high, with a 27 in by 27 ft roll, a 21 in repeat and the same 4 in trim. Straight match needs 2 rolls. Half drop alternates between 105 in and 126 in drops, and those longer drops stop fitting three to a roll, so it needs 3. The page says so: Half drop costs 1 extra roll: 3 instead of 2.

Sometimes the answer is nothing at all. On the 12 ft wall above, half drop still needs 3 rolls, and the page prints No penalty.

How much is left on your last roll?

Leftover paper matters for two reasons: repairs later, and whether you really need that extra roll. So the result tells you how much of your last roll goes unused, and how many more whole drops it could still give you before it's down to offcut.

On a straight match with a pattern repeat, it also shows how much of every drop is offcut. In the 12 ft example, 5 in of each 105 in drop goes to lining up the pattern, which is 4.8%.

Do doors and windows reduce the rolls?

No. Add each door or window as a count and the area of each one. They come off the papered area, but they don't change the roll count.

That's deliberate. You still hang a full drop beside a door and cut around the frame, so an opening rarely saves you a drop. The papered area line says so next to the figure, so it's clear why subtracting a door didn't move the total.

Where does the trim allowance come from?

The 4 in trim allowance follows common decorating advice. Screwfix's wallpaper guide adds 10 cm for trimming the top and bottom of each strip, and WallpaperBuddy says to add 4 in (100 mm) to the wall height. Change it if your installer works to a different allowance.

Everything else on the page follows from the drop method above and exact unit conversions (1 in = 2.54 cm, 1 yd = 36 in). The default roll is 20.5 in by 11 yd. Roll width, roll length, repeat and trim are all editable, in inches or centimeters, yards, meters or feet.

What this doesn't do

It won't price anything or recommend a paper, brand or supplier. It doesn't handle ceilings, staircases, dormers or sloped walls: a wall here is a width and a height. It doesn't add a waste percentage, because it counts real drops instead. If you want a spare roll for repairs, add it yourself. See our note on how much waste to add. If you're painting the rest of the room, the paint calculator does the same job for paint, and the rest of our home calculators are one click away.

Before you order

This is an estimate for planning. Rolls from different dye lots can vary in shade, so buy everything from one batch, and confirm quantities with your supplier before you order.

Wallpaper calculator FAQ

Related tools

For paint, use the paint calculator. More material calculators are on the home projects page.