Instructions
Enter the start year, begin balance, how much you'll invest each year, and the interest rate you expect to earn.

Click the Forecast button.

Once the forecast is created, click update to change the interest and/or investment amount for any year. If you check "Updates Fill Down" your changes will be applied to all subsequent years.

For example, you could generate the forecast with your planned investment (say $1000 per year) and your expected annual interest rate (say 10%).   Then at the year you expect to retire, change the investment amount to a negative number (indicating that you will now be withdrawing from your nest egg). And you could change the interest rate to a lower one (say 7%) since you may have your money invested more conservatively at retirement.

You now know when you can retire and how long your portfolio will last you after you retire.