There are four factors that are taken into consideration in determining whether or not a use falls within the fair use exception. They are:

• the purpose or character of the use: is your use non-profit, educational, personal, parodic, commercial?
  
  
• the nature of the work being used: is your use factual or imaginative, or a mixture? Is it published or unpublished?
  
  
• the amount of the work being used, and its substantiality in relation to the whole: will you use a small or large amount? is the part you use central and essential?
  
  
• the effect of the intended use on the market: will your use tend to diminish the market for the original?

Each of these factors carries weight in deciding whether the use you plan is fair use. To assess how they balance out in your own situation, use the fair use checklist.