This is a great question. I would be living in the US and probably would travel a bit. Taking into account personal taxes, a home, maintenance, taxes, insurance on the home, etc. Also accounting for all utilities, groceries, health insurance, taxes, entertainment, charity, gifts, clothing, etc. is important.
In addition, it's important to remember that health care costs increase substantially as time passes & as we age. There is a great likelihood that we will need medications at some point, possibly for the rest of our lives. All this being said, my personal minimum would be at least $9 million USD as I prefer to clear at least six figures after taxes annually.