A traditional retirement calculator is used to ascertain the future value of your retirement savings and also helps to know how much extra savings per month you require in order to reach your retirement goal. The actual results may depend on certain factors like, your age, your monthly contribution towards such funds, rate of return on the investment and your age after retirement.
Generally, the calculator just gives an idea of the need and quantity of saving for retirement. Many of the people have backup plans also, like along with investing in retirement funds, they will also have backup vehicles like FDs, LIC, etc. The important aspect for starting saving for retirement is the quantification of money required by you for retirement. This essentially depends upon your current gross salary and time left for your retirement. You may include your spouse's retirement all along.
The goals may also depend upon retirement income you expect to receive from social security pension schemes and private pension schemes. The amount expected to be received by you under such schemes and cost of living adjustments included should be known by you. Along with this, you have to calculate the savings you have already accumulated for your retirement and average rate of return expected to be received by those funds.
If you are planning to sell your house and move somewhere else (maybe rented premises) in order to have sufficient funds for your post retirement life, you must know the value of the house (current value as well as the expected resale value). Your home being an expensive property may contribute better for your post retirement life financial requirements, if you are willing to draw from home equity.
And in the end, your expected lifespan after retirement needs to be ascertained so that proper calculation of requirement of funds can be done. Your stock investments may also have to be anticipated as per your risk taking capacity.
So basically, one should ascertain all the above discussed points and fill in the calculator so that a proper estimate can be drawn out of the input and the retiree has a well calculated financial support post retirement.