Koolau
Give me a museum and I'll fill it. (Picasso) Give me a forum ...
4% of $1M = $40,000. You can withdraw 4% of you portfolio per year. It doesn't matter whether you take it in dividends, capital gains, IRAs or Roths.
Actually it does, a little, because of taxes, but that is the general idea.
The guide also allows you to raise your starting 4%, by the yearly inflation rate. 1st year $40,000, inflation 3% 2nd year, then $41,200 inflation 4% 3rd year, then $42,848.
Two studies about the 4% guide.
https://kyestates.com/wp-content/uploads/2015/02/Bengen1.pdf
And I always add FireCalc. Spend some time with it. And learn what it is doing.
https://firecalc.com/
There are lots of threads on the 4% rule and withdrawal rates. Good idea to become completely familiar with them. Here's a very old one to start. https://www.early-retirement.org/forums/f28/4-rule-14135.html