Check out the best free online Monte Carlo simulation I’ve seen.  It is even better than some commercial simulators I’ve used. It allows you to put in individual cash flows and allows a variety of spending policies (e.g., Guyton style).

For example, it can support not receiving inflation bumps during down years, unless
you already have reached some floor (e.g., 80% of initial spending).

Some weaknesses

  • The biggest one, and a deal killer for professional use, is you can’t save scenarios to a file. This means you need to reenter information from scratch every time you restart the program.
  • It takes a fairly simplistic approach to taxation (i.e., it doesn’t know all the Social Security taxation rules. The order it uses assets is fixed (taxable, tax deferred, tax free).

With that said this is the first free online tool that provides professional level flexibility.