The lady at the wallpaper store probably knows best. She's looking at the repeat pattern and can make a better calculation.

Your paper has a drop match pattern and the repeat is 27 inches; don't go only by your square footage, with a pattern such as this one there's a lot of waste for an optimum installation. Since you are hiring a professional installer, question him on the amount he told you, they usually err on the side of too much and with reason; if you run out, even by half a strip, there's no guarantee you could get the same dye lot. Thibaut is special order I think.

You might as well have leftover for future repairs, who knows ?

So how do we know that the drop match is 27 inches? How long is your bathroom. How wide is your bathroom? Did you arrive at the 27 feet by adding the four walls? If so, then multiplying by the 8-ft ceiling is correct. JMHO, but whoever wants to sell you 7 double rolls is wanting to sell more and whomever told you 3-1/2 double rolls (or 7 single rolls) is probably wrong. I think 5 double rolls is about right. Each wallpaper bolt (2 single rolls in most cases, 3 in very odd cases) will tell you what area in square feet it covers. Now if you have tile on the walls, you can subtract for that. If you have doors, windows, you can subtract for that.

I just did a friend's 240 square ft bathroom using 5 double rolls and she had a 23-inch repeat. We had paper left over, about 1 double roll.

Another factor is the paperhanger. Some will try to save your paper, whereas others will cut one length at a time and not care about wasting it. Good paperhangers, all, does not matter, will waste or save.

I am going to say your wallpaper store probably is the most correct. Most companies encourage you to buy more for waste as sometimes, even experienced paper hangers will measure wrong, cut wrong, etc., and then if you have to order more paper, there is that chance the dye lots will not match.

Once you figure out the correct amount to buy, I would still get a little extra in case you ever need it since patterns are frequently discontinued. Trust me, I found out the hard way how difficult it is to track down discontinued wallpaper.

So how do we know that the drop match is 27 inches?

She gave the name of the paper and the manufacturer. The info is on the manufacturer's website.

Thanks everyone for your help! I know I shouldn't have second guessed the lady in the paint/paper store, I was just surprised by the variance in estimates as to amounts needed. Thanks graywings for looking up the drop match, I should have included that info w/my question. As a newbie to the world of wallpaper, I appreciate everyone's advice.

Friendly, happy and light colors nursery wallpaper creates a warm atmosphere of well-being, but it doesn't always have to be classic pink and blue! And don't limit your choice to pastels, because babies mostly see primary colors, so baby room wallpaper https://www.wallmur.com/wallpaper/nursery-wallpaper baby wallpaper should be chosen following the advice of professionals. A wall featuring, for example, yellow wallpaper with a pattern/motif depicting friendly animal faces could be perfect for a child's room.