Wallpaper Calculator

The formula

Coverage and yield assumptions

The default roll is the common US double roll: 20.5 in wide × 33 ft long (about 56 sq ft). European rolls are typically 53 cm × 10.05 m (0.53 × 10 m, about 5.3 m²); switch to metric and enter 53 cm and 10.05 m. Always confirm the width, length and repeat on the label of the paper you choose.

Understanding pattern repeat and match

The repeat is the vertical distance before the design starts over. A straight match lines up across strips at the same height; a drop match (half-drop) shifts every other strip by half the repeat. In both cases each strip needs extra length so the motif lands correctly, and the safest estimate adds one full repeat per strip, which is what this calculator does. Random-match and solid papers have no repeat, so enter 0.

Measuring the wall

Measure the width of each wall you will cover and add them together. Do not subtract doors or windows unless they are very wide: strips above and below openings are cut from full drops, and pieces rarely come out even. Measure height at several points because floors and ceilings are rarely perfectly level, and use the tallest figure.

Buy from one batch

Rolls are printed in runs, and colors shift slightly from one batch (dye lot) to the next. Check that every roll carries the same batch number and buy one extra roll for repairs. Many shops will take back unopened rolls; very few can match a lot months later.

Hanging tips

• Start at a plumb line, not a corner; corners are rarely square.
• Book pasted papers for the time the label says so they expand before hanging.
• Prime walls with a wallcovering primer to make future removal easier.
• Trim with a sharp blade and change it often.

Common mistakes to avoid

• Estimating by square feet alone and ignoring the pattern repeat.
• Buying rolls from different batch numbers.
• Starting the first strip in a corner without a plumb line.
• Skipping the primer, which makes the paper hard to remove later.
• Stretching pasted paper to close a gap, which leaves seams that open as it dries.

Waste factor

10% is the default for trimming top and bottom and for the odd mis-cut. Use 15–20% for large repeats over 20 in, rooms with many openings, or your first wallpaper project.

Imperial and metric

Switch the toggle above the inputs to enter ft ↔ m, in ↔ cm. The page converts metric entries to imperial before calculating, using NIST factors (1 ft = 0.3048 m, 1 in = 2.54 cm), and shows key results in both systems.

Worked examples

Bedroom, no repeat

Inputs: total wall width to cover 40 ft; wall height 8 ft; roll width 20.5 in; roll length 33 ft; pattern repeat (0 if none) 0 in; waste factor 10%.

Result: You need 7 rolls of wallpaper.

• Units to buy (rounded up): 7 rolls
• Strips needed (no waste): 24
• Strips with waste: 27
• Strip length incl. repeat: 96 in
• Full strips per roll: 4
• Wall area: 320 sq ft (29.7 m²)

Accent wall with 21 in repeat

Inputs: total wall width to cover 14 ft; wall height 8 ft; roll width 20.5 in; roll length 33 ft; pattern repeat (0 if none) 21 in; waste factor 10%; cost per unit $85.

Result: You need 4 rolls of wallpaper.

• Units to buy (rounded up): 4 rolls
• Strips needed (no waste): 9
• Strips with waste: 10
• Strip length incl. repeat: 117 in
• Full strips per roll: 3
• Wall area: 112 sq ft (10.4 m²)
• Estimated material cost: $340.00

Tall dining room

Inputs: total wall width to cover 52 ft; wall height 9 ft; roll width 20.5 in; roll length 33 ft; pattern repeat (0 if none) 12 in; waste factor 15%.

Result: You need 12 rolls of wallpaper.

• Units to buy (rounded up): 12 rolls
• Strips needed (no waste): 31
• Strips with waste: 36
• Strip length incl. repeat: 120 in
• Full strips per roll: 3
• Wall area: 468 sq ft (43.5 m²)

Quick reference for common sizes

The table repeats the first worked example at smaller and larger sizes, keeping every other setting the same, so you can see how the wallpaper calculator result scales.

Limitations

The math assumes full-height strips on flat walls. Stairwells, sloped ceilings and accent panels with many cuts need a strip-by-strip plan. Murals and panel sets are sold by size, not rolls.