finance charge on credit card

[min]

I need a formula that I could use to figure out finance charge on a monthty
basis on a credit card.

 

[BrianB]

Not sure exactly what you want.

Say Interest Amount in A1 and Total Amount in B1
Interest Amount/Total Amount times 100 = percent rate
in C1 put formula =A1/B1
(format C1 as percent)

Say Total Amount in A1 and Percent Rate in B1
Total Amount times Percent Rate divided by 100 = Interest Amount
format B1 as percent
in C1 put formula = B1* B1