Read the formula and variables
A constant positive payment begins one period from now and r is positive.
| Input | Meaning |
|---|---|
| C | Equal payment forever |
| r | Positive discount rate per payment interval |
Check a stated example
A constant payment of 4 at 8% per period gives time-zero value 50.
The amounts in the example are synthetic. Keep the original precision through the calculation and round only the displayed result.
Check the domain and timing
The positive-rate condition supplies convergence of the infinite discounted stream. A finite-horizon annuity is a different pattern.
A changed date, payment pattern or quotation convention can require a different expression even when the numbers look similar. Identify those features before calculating.