Let's clarify some of the concepts used with this app: Present Value = Principal amount or the Initial investment. How much money would be needed to produce the Future Value. Interest Rate = An interest rate is the rate at which interest is paid by borrowers (debtors) for the use of money that they borrow from lenders (creditors). Specifically, the interest rate is a percentage of principal paid a certain number of times per period for all periods during the total term of the loan or credit. Future Value = The final amount of money you want to gain in the end. E.I. Rate = Effective Interest Rate is the interest rate on a loan or financial product restated from the nominal interest rate as an interest rate with annual compound interest payable in arrears. Each calculator has a Calculate and Clear Button.