Wallpaper Calculator

Enter your room dimensions and roll specs to find out exactly how many rolls to buy. Results update instantly.

Room Dimensions

ft
ft
ft

Doors & Windows

Custom opening size (optional)

Enter a non-standard opening and add it to the deduction. Leave at zero to skip.

ft
ft

Roll Specifications

in
ft
in
$
Rolls to Buy
5
rounds up from 4.2 usable rolls
Total Wall Area
352 sq ft
Net Coverage Area
307 sq ft
Usable Area / Roll
—
Waste
—
Openings Deducted
—
Total Cost
—

How to Use This Wallpaper Calculator

  1. Measure the room — enter the length, width, and ceiling height in feet. For rooms with accent walls only, enter the total width of the walls you plan to paper as the combined perimeter divided by two, keeping height as-is.
  2. Count openings — enter the number of standard doors (3×7 ft) and windows (3×4 ft). Use the custom opening section for arched doorways, sliding glass doors, or any non-standard size.
  3. Enter roll specs — the defaults (20.5 in wide, 33 ft long) match the most common US single roll. Check the label on the roll you plan to buy and enter the exact values.
  4. Set the pattern repeat — enter 0 for solid colors, grasscloth, or textures without a repeat. For patterned wallpaper, measure from one motif to the next identical motif vertically and enter that distance in inches.
  5. Add a cost per roll — optionally enter the price per roll to see your total material budget.

How the Wallpaper Calculation Works

Estimating wallpaper is more involved than estimating paint because rolls have fixed dimensions, every strip must reach from floor to ceiling, and patterned paper loses material to alignment. The calculator works through five steps.

Step 1: Total Wall Area

The four walls of a rectangular room have a combined area equal to the perimeter multiplied by the height:

Total Wall Area = 2 × (Length + Width) × Ceiling Height

For a 12×10 ft room with 8 ft ceilings this equals 2 × (12+10) × 8 = 352 sq ft.

Step 2: Deduct Openings

Doors and windows reduce how much wall you need to cover. However, the strips that run past a door or window still use the full strip from floor to ceiling — the savings come only from the width of the opening. The calculator deducts 80% of each door area (3×7 = 21 sq ft, so 16.8 sq ft each) and 50% of each window area (3×4 = 12 sq ft, so 6 sq ft each). This conservative deduction reflects real-world installation where strips are cut around the opening but neighboring strips are wasted on those edges.

Step 3: Usable Area Per Roll — No Pattern

When there is no pattern repeat, you can cut the roll into strips of exactly the ceiling height with minimal waste:

Strips per Roll = floor(Roll Length ÷ Ceiling Height)
Usable Area per Roll = Strips per Roll × Roll Width (in ft)

A 33 ft roll on 8 ft ceilings yields 4 full strips (4×8=32 ft used, 1 ft scrap) at 20.5 in (1.708 ft) wide, giving about 13.67 sq ft of usable wall coverage.

Step 4: Usable Area Per Roll — With Pattern Repeat

When there is a pattern repeat, each strip must be cut so the pattern aligns with the adjacent strip. This requires starting each strip at the same point in the pattern cycle. The effective strip length therefore becomes the ceiling height rounded up to the next multiple of the repeat:

Effective Strip Length = ceil(Ceiling Height ÷ Repeat) × Repeat
Strips per Roll = floor(Roll Length ÷ Effective Strip Length)
Usable Area per Roll = Strips per Roll × Strip Actual Length × Roll Width

For an 8 ft ceiling with a 24-inch (2 ft) repeat, each strip needs ceil(8/2)×2 = 8 ft, so there is no extra waste in this case. But for a 21-inch repeat, each strip needs ceil(96/21) = 5 repeats = 105 inches = 8.75 ft, meaning 8.75 ft is consumed from the roll for each strip that covers 8 ft of wall.

Step 5: Rolls Needed

Divide the net coverage area by the usable area per roll and round up to the next whole number. Rounding up is critical — you cannot use a fraction of a roll for a full-height strip.

Rolls Needed = ceil(Net Coverage Area ÷ Usable Area per Roll)

Understanding Waste Percentage

The waste percentage shown is calculated as the difference between the gross area covered by all the rolls you buy and the net wall area you actually need to cover, expressed as a percentage. A number between 10% and 25% is typical for a solid or small-repeat pattern. Large repeats (18 inches or more) can push waste above 30%. Buying an extra roll as insurance is always recommended for patterns with repeats above 12 inches.

Tips for a Professional Result

Always start measuring from the most prominent wall and work around the room so any mismatch ends in an inconspicuous corner. Use a plumb line or laser level on every strip — walls are rarely perfectly vertical. Soak paste-the-wall papers for the time specified by the manufacturer before hanging. Match the pattern at eye level first, then adjust toward the ceiling and floor. Keep one extra roll from the same batch code for repairs — dye lots vary between production runs and a later purchase may not match.

Frequently Asked Questions

First calculate the total wall area by adding up the area of all four walls (2 × (length + width) × height). Subtract the area of doors (roughly 21 sq ft each) and windows (roughly 12 sq ft each) to get the net coverage area. Then determine the usable length per roll — this is the roll length divided by the ceiling height, rounded down to a whole number of strips, multiplied by the roll width. Divide the net coverage area by the usable area per roll and round up to get the number of rolls to buy.
A pattern repeat is the vertical distance between identical points in a repeating wallpaper design. When hanging patterned wallpaper, each strip must be cut so the pattern aligns with adjacent strips. This means you lose up to one full repeat per strip as waste. For example, a 24-inch pattern repeat on 9-foot ceilings adds roughly 24 inches of unusable material per strip. The calculator accounts for this by reducing the usable length per strip to the largest multiple of the ceiling height plus the repeat that fits within the roll length.
In the United States, the most common single roll is 20.5 inches wide and 33 feet long, covering approximately 56 square feet gross. European double rolls are typically 20.5 to 27 inches wide and 16.5 to 33 feet long. Always check the label on the roll you plan to buy and enter the exact dimensions into the calculator for the most accurate estimate.
Professionals typically recommend buying 10 to 15 percent extra to account for trimming errors, damaged strips, future repairs, and pattern waste not fully captured by the repeat calculation. This calculator rounds up to whole rolls automatically, which already provides a small buffer. For complex patterns with large repeats (over 18 inches), consider adding one additional roll beyond what the calculator recommends.
You measure the full wall perimeter including door and window openings, then subtract their areas. However, the strips that run over doors and windows still consume material from the roll up to the ceiling height. The best practice — and what this calculator does — is to deduct 80% of each door area and 50% of each window area from the net coverage area, which reflects how much material is actually saved by those openings in a real installation.