Banners can be made any size.

Here is a list of common sizes and prices

4' Tall Banners - $12 Linear Foot

8' x 4' = $96     5' x 4' = $60

7' x 4' = $84     4' x 4' = $48
6' x 4' = $72     4' x 3' = $36

3' Tall Banners - $10 Linear Foot

8' x 3' = $80     5' x 3' = $50

7' x 3' = $70      4' x 3' = $40

6' x 3' = $60      3' x 3' = $30