What is postage on 7 sheets of paper?

you can put up to 3 pieces of paper in a business size envelope for 1 postage stamp

I remember this because I went to a correspondence High School.

Also:

"1-3 just one. 4-borderline, 5-two. Note that the second ounce costs less than 42 cents.

This really depends on what weight paper you use so if you want to make sure, take the letter to the post office where just about all of them have an automated terminal where you can weigh and buy proper postage. As a tip, they seldom check the weight. If it is in a standard envelop and it is not bulging, they will let it through." (From Yahoo: Yahoo.com/question/index?qid=20090225184741AAP6Xqm">http://answers.Yahoo.com/question/index?qid=20090225184741AAP6Xqm)