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Library ROI Calculator

On our Donate page you can calculate the approximate value you've received from CPL in the last year. This calculator is similar to those used at other libraries, with a few important differences.

Calculating Books and DVDs

Most library use calculators have you put in the number of books (or DVDs) that you checked out in some period of time. The value per book tends to range from $15 to over $25. That cost reflects the average cost of buying a book, not the average value of checking out a book.

Instead, we simply have checkboxes. If you checked out a book in the last year, you check a box. Same for DVDs. The checkbox reflects the annual cost of Netflix (and similar services for books, which exist but tend not to last). In any year, you could use Netflix to borrow a virtually-unlimited number of DVDs; the same as in the library. This more-accurately reflects the actual value you derive from using the library.

Behind the Scenes

Our calculator is a slightly-tweaked version of our open source library-roi-calc project. The project lives on github and can be cloned, forked, modified, and used by anyone. If you'd like to contribute to the project, you can submit pull requests to update the repository.

Technical details are available in the readme, but here are some ways that this project is a technical improvement on previous calculators:

  • Calculator updates as you type
  • HTML5 "number" <input> elements for easy number entry
  • Event listeners to separate content from behavior
  • Ability to have multiple calculators on one page
  • <output> elements and other good HTML semantics
  • Intuitive data- attribute way to store/use calculations
  • Built using the popular jQuery library
  • Inline help text with pure-CSS icons

I hope you get good use out of this project. It was a lot of fun to create the calculator, and I'm proud of how it turned out.