A simple online annuity due payment calculator is used to calculate equal cash flow or payment of a series of cash flows when the future value is known. Payments made under an ordinary annuity occur at the end of the period while payments made under an annuity due occur at the beginning of the period. In the below future value of an annuity due calculator, enter the values of future value, the rate per period and number of periods to know the resultant value.