What real rate of return should I assume when projecting my FIRE timeline?

FIRE math should use real (inflation-adjusted) returns so your target and spending stay in today's dollars. A common, reasonably conservative assumption for a stock-heavy portfolio is about 5% real, roughly a 7% to 8% nominal return minus 2% to 3% inflation. Vanguard and other research houses publish long-run capital market forecasts you can compare against.

More cautious planners use 4% real; optimists use 6% or 7%. The key is to run multiple scenarios rather than betting your freedom on one rosy number, and to recognize that early-year returns matter disproportionately because of sequence risk. Because your assumed return heavily swings the projected date, always check how your plan holds up under a lower-return case before you commit to a target date.