Forget Google, you'll be using poolmath for everything. You need to learn it, and its stupid easy, so get out of your own head, and get to playing with poolmath.
I will also suggest you upgrade to premium for $8 **a year**. Not only can you save your test logs to spot trends, we can see them too. So you get some of the greatest minds in poolcare going over your history anytime you have something chemistry related going on. At least for the first year, its worth every penny, tenfold.
Use a general measurement and guess the gallons. For a square its length X width X average depth X 7.481 gallons per cu ft. A circle is 3.14 X radius (half the diameter) X radius (again) X average depth X 7.481 gallons per cu ft.
Even if it's 1000 gallons, 1/25 will barely make a dent in anything, but it's always best to start as close as we can.
I thoroughly enjoy my pool, and you're amongst your people now. Lol. If it wasn't for the going and getting bleach, I wouldn't mind adding it everyday. It's the going and getting part I can't stand.