I never buy just "exactly" what I need for this very reason. I buy a minimum of 1/2 yard. That way I have enought to allow for printing errors, rolling distortion from the manufacturer. Very seldom will a shop allow for more than 1" inch or a thumb when cutting. If you are getting from a chain store, they usually cut EXACT or charge you for the extra inches.. as they do have charts they use by the inch, so their inventory is not off.
Any excess left over can be used for scrap quilts, bags, pincushions, etc. If I am buy for an unknown project, I buy at least 2, I do sometimes buy 1 yard but only if the fabric is very expensive and I can buy a co ordinate fabric to blend with it.