Before you calculate
FIRE is a savings-rate and spending problem.
FIRE means Financial Independence, Retire Early. The goal is a portfolio large enough that paid work becomes optional or less central.
Lean FIRE uses lower spending, Fat FIRE uses higher spending, Barista FIRE keeps part-time or freelance income, and Coast FIRE means earlier savings may grow enough for a later retirement goal without the same contribution pace.
The estimate depends on savings rate, spending target, portfolio return, withdrawal assumptions, taxes, CPP and OAS timing, pensions, and how many years the portfolio must bridge before public benefits start.