Calculate FIRE number then adjust for inflation? If I want to retire in 20 years, assuming 15% inflation, that would be 1/16th purchasing power in 2 decades.

(Rule of 72, divide by inflation rate and that is when money is cut in half, every 5 years at 15%)

Multiply monthly expenses by 300, then multiply by 16 (to retire in 20 years). I’ll need $100M, which is about 4x what I thought I would need.