[baccredited]

Sorry - if you sign up this site will allow you to input your monthly savings, spending, and net worth. Then it will estimate the amount of time before you achieve Financial Independence. It is free. I'm a big fan.

https://lab.madfientist.com/pages/help

[shostack]

Any recommendations for a free spreadsheet version or open source version that doesn't require giving my financial data to yet another 3rd party and tying it to a unique identifier via login?

[rwol]

Here's a login-less one that looks like it doesn't make any network calls with the data you enter: https://networthify.com/calculator/earlyretirement

[fjsolwmv]

http://firecalc.com is the best.