How do I calculate wallpaper rolls?

Calculate the total wall area: 2 × (length + width) × height. Subtract doors (about 21 sq ft each) and windows (about 15 sq ft each). Add 10–15% waste for pattern matching, then divide by the coverage per roll. Round up.

What is the difference between single and double rolls?

A single roll covers about 28 sq ft. A double roll is two single rolls bonded together and covers about 56 sq ft — most commonly sold this way because longer continuous strips reduce seams. Always check the actual coverage on your specific product label.

How much extra wallpaper should I buy?

Add 10% for solid-color or small-repeat patterns. Add 15% for medium repeats (under 19 inches). Add 20% or more for large floral or graphic repeats. Pattern repeat is always listed on the wallpaper sample.

Should I subtract doors and windows?

Yes — subtract any opening larger than 10 sq ft individually. Small windows or transom openings can be ignored because the surrounding waste percentage will cover them. Our calculator uses standard sizes: 21 sq ft per door and 15 sq ft per window.

How do I match wallpaper patterns at seams?

Hang strips so that the pattern aligns horizontally across seams. Drop-match patterns require you to alternate every other strip, which doubles the pattern repeat waste. Always order extra to allow for at least one strip you can recut if a match fails.

Can I use the same calculator for wall paneling or wainscoting?

Yes — wall paneling and wainscoting are sold by panel or linear foot. Calculate your wall area the same way, then divide by the coverage of your specific panel. For wainscoting that covers only the lower 3–4 feet, multiply perimeter × wainscot height instead of full wall height.

Wall Area Calculator

Wallpaper Calculator

Calculate exactly how many wallpaper rolls you need for any room — wall area is computed automatically from length, width, height, and standard openings.

Length (ft)

Width (ft)

Height (ft)

Doors (#)

21 sq ft each (standard)

Windows (#)

15 sq ft each (standard)

Roll Type

Pattern repeat (adds 5% waste)

Results

Gross wall area416.0 sq ft

Doors + windows-51.0 sq ft

Net wall area365.0 sq ft

Net + 10% waste401.5 sq ft

Roll coverage56 sq ft / roll

Rolls to buy8 rolls

For large pattern repeats (over 19 in), increase waste to 20% or more. Solid-color and small-repeat patterns can use the standard 10–15%.

Wall Area Formula Explained

The wall area of a rectangular room is the room perimeter multiplied by the ceiling height, minus the area of doors and windows. The full formula is:

Wall area = (2 × Length + 2 × Width) × Height − (Doors × 21) − (Windows × 15)

For a 12 × 14 ft room with 8 ft ceilings, 1 door, and 2 windows:

Perimeter = 2 × (12 + 14) = 52 ft
Gross walls = 52 × 8 = 416 sq ft
Openings = 21 + 2 × 15 = 51 sq ft
Net wall area = 416 − 51 = 365 sq ft
With 10% pattern waste = 401 sq ft
÷ 56 sq ft per double roll = 7.16 → 8 rolls

Wallpaper Pattern Match Types

Random Match

No alignment needed — strips can hang in any order. Solid colors and small textural prints. Lowest waste, around 10%.

Straight Match

Pattern aligns horizontally across every seam. Repeats are listed on the label. Plan 10–15% waste depending on repeat size.

Drop Match

Alternating strips shift the pattern down by half the repeat. Doubles the effective repeat — budget 15–20% waste.

Frequently Asked Questions

Related Calculators

Wallpaper goes hand-in-hand with paint trim and ceiling work. Estimate it all in one place.

Sources

The figures on this page are based on data from these authoritative industry sources.

The Home Depot Buyer’s Guides — Retail price ranges for flooring, paint, and finishing materials.

Wallpaper Calculator

Results

Wall Area Formula Explained

Wallpaper Pattern Match Types

Random Match

Straight Match

Drop Match

Frequently Asked Questions

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Sources