It is a very good idea to use a pension annuity calculator when you first get a job, as it can show you how much money you will have saved toward retirement and your pension. However, you should not just use it once. Every time that you are promoted to a new position, you need to use it again. After all, your income will have changed and your retirement plan may have changed. In order to have an accurate idea of how much money you are going to have when you retire, you need to use the calculator repeatedly.