Try using Code Beautifier. You input the code and it formats it for you. There are many other sites like this one so check around and see which one you like best.
If you want to use a Sublime Text plugin, try CSS Format by mutian.
EDIT: As said by Imran Bughio, CSS Beautify is another site like Code Beautifier.
EDIT 2: As noted by Beginner, CSSLisible is another option.