. I sorry Guys but unless you are using multiply Nozzles and 50 different Products at Different speeds, I feel you are over thinking a simple process. From the Number Given you are able to spray 1.65 acres or just under 72 K. from a 60 gallon tank at a rate of 36.4 Gallon per acre. Calibration now becomes very simple. 72 is the Magic number for a full tank and a half tank would have a magic number half that or 36. Read your label and even write the per thousand rate on the Pesticide Jug. Now just Multiply that per thousand rate times your permanent Magic number of 72 for a full tank or 36 for a half tank, 18 for a 1/4 tank etc. OK put a fork in me because I am done with this thread. I don't feel I can add any thing more that could be absorbed. .