When you download the calculator, you'll find a gray box at the upper left. The numbers in the gray box are supplied by Etsy. You can change any of them, if Etsy increases their listing fees, sales commission, or card processing fees--the calculator will still work.
There are actually two calculators. The first lets you input what you are charging for an item and how much you are requiring for shipping. It will then calculate what your net will be, after fees and shipping are subtracted.
The second calculator allows you to enter the amount you would like to receive for an item and how much you plan to charge for shipping; it then calculates what you should charge in order to receive that net amount, after fees and shipping.
You can check the two calculators against each other. Only the cells that should take inputs will allow your input. There are also a few notes, just click on the small red square at the upper right of any cell that has one, for additional information.
I hope it saves you as much time as it does me!
You'll be provided with an image. Look to the top of your screen for download icon/link.