A few little bits better than the 4% rule of thumb.
Here is a step-by-step to know (when you can stop working for fiat) if you have enough of a baseline asset value to sell assets for living expenses and at least maintain your baseline asset value over the future (number don't go down).
This is based on averages, such as extrapolating average historical performances into the future. I only know the wheels will keep spinning. No one knows how they will spin at any given moment. Typically, most of the time its a fast and accelerating wheel spinning (10% average annual return on investment) with some times of quick and short wheel spinning (deflationary times, systemic margin calls, notable drawdowns, reaching for collateral, etc.) and some times of slow and decelerating spinning (stagflation). You have to be able to survive all of the above scenarios for extended periods of time. You could be a "millionaire" now but string 5 deflationary years in a row and it's chaos a.d. (must keep printing fiat to avoid chaos a.d.).
1.
Find your net worth (assets minus debt)
example: 401k plus savings plus bitcoin minus mortgage and minus car notes)
2.
track networth back at least 5 years and find the average annual compound growth rate (aacgr)
example: search/ask/cc Google "what is the average annual compound growth rate for a starting net worth of (...enter your starting point net worth here...) (...enter your starting point of how many years ago here...) years ago and a current net worth of (...enter your current net worth here...)
3.
Find assumed future aacgr.
If answer from #2 is greater than 10% use 10% as the assumed future aacgr. Otherwise, use your calculated aacgr from #2 as your assumed future aacgr.
Current net worth must be greater than starting point net worth.
4.
Find maximum allowable annual spending (maas).
Multiply current net worth times assumed future aacgr from #3 to equal maas.
example: multiply 1 million net worth times 10% assumed future aacgr equals 100,000 maas.
5.
Find your last year total spending and living expenses including amounts charged to credit cards.
!!!!! To stop working and at least maintain your current baseline net worth!!!!!, your last year of spending must be below your maas value found in #4 above.
6.
Life happens. Track and reassess regularly. You might be pleasantly surprised at the cost of health insurance after your income decreases. Check health insurance benefits available to you.
7.
This calculation assumes we are entering inflationary years ahead (decades) but periods of deflationary years are possible, especially 2 or 3 deflationary years in a row and will wreck this rough calculation. And wreck is definitely no bueno. Don't even ask what happens if your bad investment choices and poor sell timing skills are coupled with deflationary years. Don't look at me. Look in the mirror.