In common terms the future value of an annuity or regular annuity is specified by the subsequent formula:

FVA_n = A (1 + k )^{n -1} + A (1 + k )^{n - 2} + ... + A   ................................Eq(6)

A [((1 + k)ⁿ - 1)/k]

Future value of an annuity due:

FVA_n(due) = A (1 + k )ⁿ + A (1 + k )^{n - 1} + ... + A(1 + k)   ................................Eq(6)

....................................Eq(7)

= A [((1 + k)ⁿ - 1)/k] (1 + k)

Here FVA_n = Future value of an annuity that has a duration of n periods

A   = Constant periodic cash flow;

 k = Interest rate per period;

n = duration of the annuity.

The term [((1 + k)ⁿ - 1)/k] is considered to as the future value interest factor for an annuity (FVIFA_k,n). The value of its factor for some combinations of k and n are specified in the appendix at the end of this section.