Also the air density will matter when there are mass problems.like I said if someone told you that the jar is 1200 grams then you can take 80 percent of that, and then divide if I the average density. Remembers mass divided by density meet equals volume. find the average density you will need to know the density of the candy and the density of the air. If you know that then you can take 70 percent of the density of the candy times and add 30 percent are the density of the air to it which will give you the average density. Now this example assumes that the packing efficiency is 70% but it can and will be different for others.