Some of the line items in this calculation may require explanation:
Your child is probably a few years from starting college if you are looking here.
The first box asks for the number of years until they start college.
The second line asks for the number of years that you need to finance.
If you have more than one child and they are less than four years apart in age then you may want to put in the total number of years from the first one starting college to the last one leaving college.
The annual cost comes from the previous calculation.
Tuition fees tend to increase faster than other prices. Make an estimate of the inflation rate for tuition and then the general price index inflation.
The existing savings are the ones that you expect to use for college costs. Estimate the annual return that you expect to earn on these investments.
If savings are in a 529 plan then the investment gains will not be taxed.
The last line asks if you expect some of the costs to be met from other means, such as scholarships and current income.