How this FIRE calculator works
Financial independence, in this model, is a stock of invested assets large enough that a chosen withdrawal rate covers this year’s spending. The FI number is annual spending divided by the withdrawal rate. At 4% and $50,000 of spending, you need $1,250,000. At 3.5% you need more; at 5% you need less and take more sequence-of-returns risk.
Each year we add your monthly savings, apply the real return you typed, and stop when the portfolio crosses the FI line. “Real return” already nets out inflation, so spending stays in today’s dollars. The chart is a straight-line sketch: no recessions, no job loss, no Social Security, no pension. That is why the big number is labeled in years, not as a promise that work becomes optional on a calendar date.
The Trinity-study 4% rule used a 30-year retirement and a stock/bond mix that survived most U.S. historical windows. People aiming to retire at 40 may need a 50-year horizon, a cash buffer, or the willingness to cut spending after a bad decade. Use this page to see whether your savings rate even points at the right decade — then read a full plan with a professional if the number is life-changing.