FIRE calculator
Plug in your situation. The math: keep adding savings, let them compound at a real (after-inflation) return, and you’re financially independent the day your portfolio reaches 25× your annual spending — the long-standing 4% rule from the Trinity Study.
Path to FI
Solid line is your portfolio over time. Dashed line is your FI number. Where they cross is the day you can stop.
What moves the date
The first one is in your control today. The second one mostly isn’t — allocation tweaks can shift expected return modestly, but no one can promise it.
How this works
“Financial independence” here means your portfolio is large enough that a sustainable withdrawal covers your living expenses indefinitely. The standard rule of thumb — from the 1998 Trinity Study (Cooley, Hubbard, Walz) and refined since — is that withdrawing ~4% of a stock-heavy portfolio in year one and adjusting for inflation each year historically lasted 30 years in nearly every backtested window.
Real returns: the “return %” input is the return after inflation. That lets the target-spending input stay in today’s dollars and avoids a separate inflation knob. Long-term US equities have averaged 6–7% real; a globally diversified 80/20 portfolio is often modelled at 4–5% real. Pick what feels honest, not what you’d like to be true.
The 4% rule is not a guarantee. Big ERN’s extensive Safe-Withdrawal-Rate series shows that for retirement horizons longer than 30 years (e.g. someone retiring at 40), a 3.25–3.5% SWR is more defensible — try lowering the SWR input above and watch the FI number jump. Sequence-of-returns risk in the first decade of retirement dominates outcomes; nothing in this calculator models that.
For intuition, not advice. The math here assumes constant contributions, monthly compounding, and a constant real return. Real life is none of those.