Not sure if this is right forum for this question, but didnt know where to ask my question

can anybody out there figure out how many gallons of water in my pool. I know it will just be a guesstimite---but that would help. Pool guy says I have 50,000 gallons but went to 2 pool stores today and they said no-way---that that is size of olympic pool and it was doubtful my pool was that big. Need general idea so I know how much bleach to add. Fighting algae and getting no where. Pool is kinda L shaped, deep end 8-9ft deep and shallow end is 4-5 ft deep. I measured deep end 19x20 and the other part 14x18. I know there was an in between area not measured but didnt quite know how to . Hopefully this is enough info to at least get a ballpark guess, Any info would be great
Thanks