Present Value Annuity Factors
The formula for a present value annuity factor discounts a future value amount to its value in the present by using the applicable interest rate and the number of years the investment will last. For example, if you are promised $1,000 annually for the next 10 years, which you put into a savings account that pays 1 percent interest, today's value would be $1,000 multiplied by the present value annuity factor of 1 percent and 10 years ($1,000 * 9.47130) = $9,471.30. Find the present value annuity factor of 9.47130 by using an annuity factor table, and choose the factor residing at the intersection of your interest rate (1 percent) and number of investment periods (10).
Future Value Annuity Factors
The formula for a future value annuity factor compounds the amount using the applicable rate and the number of years the investment will last. For example, if you deposit $5,000 annually for the next five years in a mutual fund that paid 7 percent, how much would you have in five years? To calculate this, using a table with future value annuity factors, you would multiply $5,000 by the future value annuity factor at the intersection of 7 percent and five years: $5,000 * 5.75074 = $28,753.70.