Choosing a credit card calculator to find the total interest paid.

Crucial information: This calculator will do what is needed: http://www.consumercredit.com/CC-interestCalc.htm

Why didn't I say this in the first place?

When I first made the assignment, I just found a couple of calculators from a well-respected site that did what was needed and gave instructions for how to use them. However, since I wrote the assignment, the credit card calculator I had chosen has disappeared from that link. (That's a danger of including a "live web page" in an assignment! I didn't think about that possibility.)

Students who were using other credit card calculators from that same site were getting some results that didn't make sense to them. I'm sure they are correct calculators, but my detailed instructions weren't accurate for them.

I found a different credit card calculator seemed to me to not be as dependent on detailed instructions - and found this one. http://www.consumercredit.com/CC-interestCalc.htm In this calculator, you choose between giving a minimum percent payment and a minimum dollar amount payment. So it is easy to leave the minimum percent payment blank and just fill in the dollar amount.

I checked it by choosing an example. I chose $800, for 19% interest, and a monthly payment of $30. The calculator told me that it would take 35 months and I would pay $246.6124 in interest.

Then I created an amortization table for this same problem myself by changing the values in another amortization table I had completed. Since I had checked that amortization table in various ways, I was confident that I understood that it was correct. When it gave me the same number of months and total amount of interest paid, that gives me confidence that this credit card calculator is making correct calculations.

One of the students showed me her printed amortization table from one of the Bankrate credit card calculators. I noticed that it did show the minimum payment it was using for computations in each month and it did not remain constant for each month. So that was an indicator that the it was not doing what the student thought it was doing.

I do like the fact that the Bankrate calculators have amortization tables. That makes it very easy to check against an amortization table that I create and see if it is doing exactly what I think it is doing. Since this new calculator I chose doesn't have that, I had to get the total interest paid in my amortization table to check it against this new calculator.

I don't have time right now to figure out why the Bankrate credit card calculator did give the right answers for some of the loans and didn't for others.