Can I actually retire early?

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Plug in your numbers, run 2,000 Monte Carlo simulations, get back a probability instead of a single optimistic estimate.

How the simulation works

The calculator runs 2,000 Monte Carlo paths. Each year of each path samples a return from a normal distribution (default mean 7%, standard deviation 15% — close to the post-1928 S&P 500) and an inflation rate (default 2.5% mean, standard deviation 30% of the mean). Everything is in today’s dollars: the FIRE target, your monthly savings and your retirement spending all rise with each path’s cumulative inflation, so a 4% withdrawal rate really is 4% of the portfolio on the day you retire. Withdrawal in retirement uses the safe withdrawal rate you set; the classic 4% rule comes from Bengen (1994) and the Trinity Study.

We report two numbers. Success rate is whether you hit the FIRE target by your chosen retirement age. Survival rate is, among the paths that do reach FIRE, the share where the portfolio lasts to your life expectancy. The second one traps a lot of people. Hitting the target is one thing; sequence-of-returns risk in the first 5–10 retirement years is what actually wrecks portfolios.

All math runs in your browser. We don’t store your inputs. Source code on github.

Scenarios we’ve already crunched

If your numbers look like one of these, the article skips a few steps for you:

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