You'll want to accurately estimate the amount of wallpaper needed if you are ordering it, so you don't discover you are short in the middle of a project. At the same time, you want to avoid buying unnecessary rolls, even if they can be returned to keep your costs as low as possible. It's a good project you can plan for accordingly.
1. Calculate the area of the project.
Measure the length and height of each wall you wish to cover in wallpaper. Subtract doorways and large windows from the total length. You can round the length measurement up to the nearest half foot or foot (or meter) to make it easier to calculate.
Multiply the length and width of each wall to get the area in square feet.
Add up the area of each wall to get your total area.
Increase the total area by 15 percent to account for waste.
2. Choose the wallpaper pattern. You won't be able to estimate the amount of wallpaper needed until you know whether it has a straight match or drop pattern.
A straight pattern has either white paper or a continuous stripe of color along the edge, so that there's no pattern to match up to the next piece when you hang it. This type of pattern will require the least amount of wallpaper.
When the pattern is different along the right and left edge, you have to take the pattern into account when hanging the wallpaper. This requires cutting a piece off the top at times, so you can shift it up and match it to the pattern on the piece you just hung. This drop pattern requires ordering more wallpaper because the part you cut off the top is often wasted.
3. Look at the wallpaper packaging or on the back of the sample to find out the repeat length of a drop pattern. Measure it yourself just to be sure it's correct.
4.Verify the number of square feet each roll covers. In the U.S., a standard single roll covers 36 square feet (3.35 square meters). European standard rolls cover 29 square feet (2.7 square meters).
5. Reduce the total usable square footage on a roll to account for a drop pattern, if applicable. (If the wallpaper has a straight match, all 36 square feet are usable.) Use the following guideline to determine how much wallpaper is usable on a single roll:
A drop pattern of 0 to 6 inches (0.0 to 15.2 cm) has 25 square feet (2.3 square meters) of usable wallpaper.
A drop pattern of 7 to 12 inches (17.8 to 30.5 cm) has 22 square feet (2 square meters) of usable wallpaper.
A drop pattern of 13 to 18 inches (33.0 to 45.7 cm) has 20 square feet (1.8 square meters) of usable wallpaper.
A drop pattern of 19 to 23 inches (48.3 to 58.4 cm) leaves only half a single roll as usable.
6. Calculate the number of single rolls needed. Divide your estimated total square footage by the number of usable square feet on a roll to get the number of single rolls needed for the project.
7. Determine how many rolls of wallpaper to buy. Although wallpaper is priced as a single roll, most manufacturers sell it as a double or triple roll. If the wallpaper is sold as a double roll, divide the number of single rolls by 2. If the wallpaper is sold as a triple roll, divide by 3.