Top Shot Calculator is a fishing app to help calculate top shot or backing length. Enter in your line capacity, enter your backing, add the "lbs test" of the top shot you want and you get the yardage. Its that simple. Top shot calculator was created by a need to save money on fishing line. We needed a way to figure out how much line we needed to buy to fill all our spools. Now we know. The app has many other uses. When purchasing reels make sure they hold the amount of line you want with your braid and top shot. You can also calculate your backing if you only want a specific yardage of top shot. Want to only buy 150 yard spools of braid? Figure out how much mono to put on the reel before you add your braid. Use a line counter to help with this application.