# Wallpaper Calculator

Calculate how many rolls of wallpaper you need for any room. Accounts for doors, windows, roll size, and ceiling height with waste estimation.

## What this calculates

Avoid buying too much or too little wallpaper. Enter your room dimensions, number of doors and windows, and roll specifications to get an accurate roll count. The calculator accounts for trimming waste and standard opening sizes.

## Inputs

- **Room Length** (ft) — min 1, max 200 — Length of the room in feet
- **Room Width** (ft) — min 1, max 200 — Width of the room in feet
- **Room Height (floor to ceiling)** (ft) — min 6, max 20 — Ceiling height in feet (standard is 8 ft)
- **Number of Doors** — min 0, max 20 — Standard doors are about 21 sq ft each
- **Number of Windows** — min 0, max 30 — Standard windows are about 15 sq ft each
- **Roll Width** (inches) — min 18, max 54 — Width of the wallpaper roll (US standard is 27 inches)
- **Roll Length** (ft) — min 10, max 100 — Length of the wallpaper roll in feet (US standard is about 32 ft)

## Outputs

- **Total Wall Area** — Gross wall area (all four walls)
- **Usable Area (after openings)** — Wall area minus doors and windows
- **Rolls Needed** — Number of wallpaper rolls to purchase
- **Waste Factor** — formatted as percentage — Percentage of material that goes to waste from trimming

## Details

The calculator first determines the total wall area by multiplying the room perimeter (2 x length + 2 x width) by the ceiling height. It then subtracts approximately 21 square feet per door and 15 square feet per window to get the usable wall area that needs covering.

Each wallpaper roll is then analyzed for how many full-height strips can be cut from it (based on ceiling height plus a half-foot trim allowance per strip). The usable area divided by the effective coverage per roll gives the number of rolls needed, rounded up.

For patterned wallpaper with a repeating design, you may need 15-20% more material to align the pattern at seams. Consider ordering one extra roll beyond the calculated amount to have on hand for future repairs or mistakes during installation.

## Frequently Asked Questions

**Q: What is the standard wallpaper roll size in the US?**

A: The most common US wallpaper roll is 27 inches wide and about 32 feet long (a single roll covers approximately 72 square feet gross). European rolls are typically 21 inches wide and 33 feet long.

**Q: How much extra should I buy for pattern matching?**

A: For wallpaper with a large repeating pattern (pattern repeat of 12 inches or more), buy 15-20% extra. For small patterns or textures, 10% extra is usually sufficient. Random-match or solid wallpaper needs the least extra.

**Q: Should I subtract large pieces of furniture from the area?**

A: No. Even if a wall is behind a bookcase or cabinet, you should wallpaper the entire wall for a consistent look and to avoid problems if you rearrange furniture later.

**Q: Can I wallpaper over old wallpaper?**

A: It is generally not recommended. Old wallpaper can create bubbles, lumps, or adhesion problems. The best practice is to remove old wallpaper, repair the wall surface, and apply primer before hanging new wallpaper.

**Q: How do I handle corners and uneven walls?**

A: Always overlap wallpaper at inside corners by about half an inch and start the next strip with a fresh plumb line. For outside corners, wrap the paper around at least one inch. Never try to fold a full strip around a corner.

---

Source: https://vastcalc.com/calculators/construction/wallpaper
Category: Construction
Last updated: 2026-04-21