I design and coded this Line Capacity Calculator
in full flash few months ago and decided to share it with you guys. You can calculate topshots as well where you'll gonna need to fill up all the fields.
After months of using it i had pretty good results. The key of using this calculator is to know exactly the thickness of your line that you'll gonna intend to spool your reel with. Usually you can search online for that thickness number or if you have the spool in your hands, just take a look on that spool's label.
If you guys have any questions, feel free to ask.