For the most accurate results, you will need to do this conversion by weight and make sure all variables (sugar and peaches) are in the same unit. In this example I am using grams.   Take the weight of your peaches (pealed & sliced) and divide it by 2,000. Then multiply that number by 1700. That will give you the weight of sugar that you need for your amount of peaches in grams.   I have a B.A. in math and a pastry degree, so you can trust me with all you pastry math needs!