Author Topic: FI Projection Tool  (Read 1309 times)


  • Pencil Stache
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FI Projection Tool
« on: December 28, 2016, 05:06:58 PM »
[OP Disclaimer] I accidentally posted this on the Ask a Mustachian board earlier today, intending it for this one. Sorry for anyone finding it a duplicate

As the title of this post suggests, I was looking back in the MMM archives and began reading The Shockingly Simple Math behind early retirement in a bit more detail. I began asking questions like

  • How do I account for taxes?
  • If my income increases, but my expenses stay the same, what savings rate do I use?
  • How do I account for pensions and social security?

Since I can best understand financial models if I create them myself, I put together the attached tool this morning. It answers the above questions as well as builds in custom scenarios I can incorporate (ie. my wife is currently working part-time while the kids are young, how will her decision to return to work impact our FI date?).

Note that for simplicity, all inflationary impacts are considered in the respective salary growth rates and rate of investment returns (e.g. a 4% investment return means 4% above inflation - so 7% return with 3% inflation)

The purpose of this post is three-fold:
  • How do you estimate your FIRE date? What methodology?
  • For those number gurus out there, any flaws with my projection tool?
  • If there's no catastrophic flaws with the tool, feel free to use yourselves!