How to Measure a Room for Wallpaper

Why accurate measurements matter

Every wallpaper calculator — ours included — is only as accurate as the measurements you feed it. A perimeter that's off by a foot, or a ceiling height rounded down instead of up, can mean ordering a roll short and discovering it mid-installation when the pattern is discontinued or the dye lot no longer matches. Measuring carefully up front is the cheapest step in the entire process.

Step-by-step

1. Gather a tape measure and a notepad

   A standard tape measure and something to write on are all you need — no special tools.

2. Measure each wall at floor level

   Run the tape along the base of each wall, corner to corner. Round up to the nearest inch.

3. Add the wall measurements together

   The sum is your room's perimeter. For a rectangular room, this is just 2×(width + length).

4. Measure the ceiling height

   Measure from floor to ceiling in one representative spot. If the ceiling slopes or varies, measure the tallest point on each wall instead.

5. Note any unusual walls separately

   Alcoves, bay windows, or a fireplace breast each add their own short wall segments — measure them individually rather than estimating.

Rooms with alcoves or multiple wall types

A simple rectangular room only needs a width, length, and height. But a room with a chimney breast, bay window, or dormer alcove doesn't fit that model — those walls have their own short segments that a single width×length calculation would miss or double-count. For rooms like this, measure and enter each wall individually rather than trying to average them into one number. Our calculator's "By Wall" mode is built for exactly this — enter each wall's width separately and it sums the perimeter for you.

Common mistakes

• Measuring only one wall and assuming the opposite wall is identical — rooms are rarely perfectly square.
• Rounding ceiling height down instead of up — always round up, since a strip that's even half an inch short won't reach the ceiling.
• Subtracting doors and windows from the total — don't. You still need a full-height drop to trim around each opening.
• Forgetting to remeasure after any renovation that changed a wall's length or the ceiling height.