I find Jason's Pool Calculator to be accurate on everything but salt. Last year when I first added salt to my pool, the pool calculator said I should need 6 bags. I added 4 and had already overshot my goal. Then this year when it needed topping off, it said I would need 60 lbs. I added 40 and was over my goal a bit. Just wondering if anyone else has had this experience? I'm pretty sure my pool volume estimate is pretty close because, like I said, all other chemical additions come out right based on the calculator. I use the Aquacheck test strips.