How do you tell how many tons is my airconditioner?

If you know the capacity of your air handler you can guess at the tonnage. You can also sometimes find it by looking at the last two digits of an air handler model number, 018 = 1.5 tons, 024 = 2 tons, 030 = 2.5 tons, 036 = 3 tons, 040 = 3.5 tons, 048 = 4 tons, 060 = 5 tons.