An annuity is a series of annual payments made at the end of each year for a fixed number of years. Annuities with payments at the end of each year are sometimes referred to as regular annuities.

## Annuity Formula Examples

Annuity formulas are used to calculate annuity values. The formula to use will depend on which components of the annuity are already known.

The listing below summarizes the various formulas to use for annuity calculations.

In all annuity formulas the following symbols are used.

- FV = Future value
- PV = Present value
- i = Periodic rate
- Pmt = Periodic payment
- n = Number of years
- LN is a natural logarithm

The example used below for each of the annuity formulas is based on the following information.

- Future value = FV = 7,335.93
- Present value = PV = 4,622.88
- Periodic rate = i = 8%
- Periodic payment = Pmt = 1,000
- number of years = n = 6

## Future Value of an Annuity

FormulaFV = Pmt x ((1+i)^{n}-1)/iExcel FormulaFV = -FV(i%,n,Pmt)ExampleFV = 1000 x ((1+8%)^{6}-1)/8% = 7,335.93

## Present Value of Annuity

## Calculate Annuity Payments based on Present Value

FormulaPmt = PV/((1-1/(1+i)^{n})/i)Excel FormulaPmt = PMT(i%,n,-PV)ExamplePmt = 4,622.88/((1-1/(1+8%)^{6})/8%) = 1,000

## Calculate Annuity Payment based on Future Value

FormulaPmt = FV/(((1+i)^{n}-1)/i)Excel FormulaPmt = PMT(i%,n,,-FV)ExamplePmt = 7,335.93 /(((1+8%)^{6}-1)/8%) = 1,000

## Number of years based on Future Value

Formulan = LN(1+FV/Pmt x i)/LN(1+i)Excel Formulan = nPER(i%,Pmt,,-FV)Examplen = LN(1+7,335.93/1000 x 8%)/LN(1+8%) = 6

## Number of years based on Present Value

Formulan = -LN(1-PV/Pmt x i)/LN(1+i)Excel Formulan = nPER(i%,Pmt,-PV)Examplen = -LN(1-4,622.88/1000 x 8%)/LN(1+8%) = 6

The other type of annuity is the annuity due where payments are made at the beginning of each year.

Annuity Formulas November 6th, 2016