Time-to-FI accelerator
Time-to-FI is mostly a function of your savings rate, not your return rate. This tool plays out the trade-off explicitly: enter what you currently save, then see how much sooner you'd hit your target if you found another 1%, 3%, 5% or 10% of income to put away each month. For the full picture with country tax, pension estimates and three flavours of FIRE, head over to the full FIRE calculator.
Your current savings rate: 37.5%
Current monthly contribution: €1,500/month
Boost scenarios
| Extra savings | New monthly contribution | New savings rate | Years to FI | Years saved |
|---|---|---|---|---|
| Baseline | €1,500 | 37.5% | 22 | - |
| +1% | €1,540 | 38.5% | 22 | - |
| +3% | €1,620 | 40.5% | 21 | 1 |
| +5% | €1,700 | 42.5% | 20 | 2 |
| +10% | €1,900 | 47.5% | 19 | 3 |
Why savings rate dominates time-to-FI
The single most surprising thing about FIRE math is that the lever that moves your retirement date the most is not your investment return. It's your savings rate. Pete Adeney made this concrete in his 2012 essay "The Shockingly Simple Math Behind Early Retirement": at a 5% real return, someone saving 10% of their take-home pay needs roughly 51 years to reach financial independence; at 50%, they need 17. The math doesn't care about your salary number, just the fraction of it that goes into the portfolio versus into your life.
The intuition is easy once you see it. A higher savings rate does two things at once. It pumps more money into the portfolio every month and it lowers the size of the portfolio you need (because your annual expenses are smaller). Both effects compound, and they compound together. Returns only work on the first one. That's why a 1 percentage point bump in savings rate moves the retirement date measurably, while a 1 percentage point bump in assumed return barely registers.
The 4% rule and why we use 25x expenses by default
The "FI number" in this calculator is whatever you type into the target field. By convention, it's set to roughly 25 times your annual expenses, which is the inverse of the famous 4% rule from the 1998 Trinity study: if you can withdraw 4% of your starting portfolio per year and let the rest keep growing, the portfolio is statistically very likely to outlast a 30-year retirement. So 25x annual expenses is the rough "I never have to work again" number.
The default 750,000 EUR target on this page assumes around 30,000 EUR of annual spending — a typical European number for a single person living in a paid-off home, or a couple sharing a frugal household. If your spending looks different, type in your own 25x figure (or your own 28x figure — Europeans often use 3.5% instead of 4% to be more conservative; that gives ~28.6x).
Sources and assumptions
- Mr. Money Mustache, "The Shockingly Simple Math Behind Early Retirement" — the canonical visualisation of savings rate vs years to FI (retrieved 2026-05-07).
- Trinity study (Cooley, Hubbard, Walz 1998) — the original Safe Withdrawal Rate paper from which the 4% rule, and its 25x expenses corollary, derive.
- 5% real default — a globally diversified equity portfolio has historically returned roughly 8 to 10% per year nominal, minus ~3% inflation. 5% is the conservative "real" number we use across this site for any FIRE-style projection. The compound interest tool uses 7% because it isn't modelling a withdrawal phase.