Wallpaper Calculator
By Taro Schenker | Updated February 11, 2026
Quick Answer: To calculate wallpaper, compute the wall area as Perimeter (ft) x Height (ft), subtract 21 sq ft per door and 15 sq ft per window, then divide by the usable coverage per roll. US single rolls cover 28 sq ft, US double rolls 56 sq ft, and Euro rolls 45 sq ft. Add 15% waste for plain wallpaper; add an extra 20% for patterned wallpaper. One quart of paste covers about 4 rolls. For a 12 x 12 ft room with 8 ft ceilings, 1 door, and 2 windows, you need about 14 single rolls.
Calculate how many rolls of wallpaper you need for your room or accent wall. Enter your dimensions, choose a roll type, and get the exact number of rolls, paste quantity, and estimated cost — including adjustments for pattern repeats, doors, and windows.
How to Calculate Wallpaper
The formula for calculating wallpaper is based on your wall area and the usable coverage per roll:
- Measure the perimeter of the room (or the length of a single wall for an accent wall).
- Multiply the perimeter by the wall height to get the gross wall area in square feet.
- Subtract openings: 21 sq ft per standard door, 15 sq ft per standard window.
- Add your waste factor (15% is recommended for plain wallpaper, 35% for patterned).
- Divide the adjusted area by the usable square footage per roll.
- Round up to the nearest whole roll.
Roll Size Comparison
Wallpaper rolls come in different sizes depending on the manufacturer and region. Here is a quick reference:
| Roll Type | Dimensions | Gross Sq Ft | Usable Sq Ft |
|---|---|---|---|
| US Single Roll | 20.5" x 33' | ~36 sq ft | 28 sq ft |
| US Double Roll | 20.5" x 66' | ~72 sq ft | 56 sq ft |
| Euro Roll | 21" x 33' | ~57 sq ft | 45 sq ft |
Pattern Repeat Guide
Pattern repeat refers to the distance between the same point in a repeating design. It directly affects how much wallpaper you need:
- No repeat (0"): Solid colors, textures, and random patterns. Produces the least waste and is easiest to install.
- Straight match: The pattern aligns horizontally at the same height on each strip. Moderate waste depending on repeat size.
- Half-drop match: Every other strip is offset by half the repeat distance. This creates more waste than a straight match.
- Large repeat (>12"): Bold patterns with large repeats can waste up to 25-30% of each strip. Budget extra rolls for these designs.
Our calculator adds approximately 20% additional material whenever a pattern repeat greater than zero is entered, on top of the standard waste factor.
Formula Summary
Wallpaper Rolls Formula: To calculate the number of wallpaper rolls needed, compute the net wall area (gross area minus openings), apply waste and pattern repeat factors, then divide by the usable coverage per roll and round up.
$$\text{Rolls} = \lceil \frac{(A_{\text{gross}} - A_{\text{openings}}) \times (1 + W + P)}{C_{\text{roll}}} \rceil$$
Wall Area Formula: $$A_{\text{gross}} = 2 \times (L + W) \times H$$ for a full room, or $$A_{\text{gross}} = L_{\text{wall}} \times H$$ for an accent wall.
Paste Formula: $$\text{Quarts} = \lceil \frac{\text{Rolls}}{4} \rceil$$ (1 quart covers ~4 rolls)
| Roll Type | Usable Coverage (sq ft) |
|---|---|
| US Single Roll | 28 |
| US Double Roll | 56 |
| Euro Roll | 45 |
Standard Assumptions: Standard door = 21 sq ft, standard window = 15 sq ft. Default waste factor is 15%. Pattern repeat (any value > 0) adds 20% extra material on top of the waste factor. Paste coverage is 4 rolls per quart.
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Estimates are for planning purposes only. Consult a qualified contractor for critical projects. Actual material requirements may vary based on site conditions, waste, and installation methods.
Pricing last verified: February 2026. Material prices vary by region, season, and supplier. Prices shown are national averages for planning purposes.