5,000 Market Scenarios, Not One Optimistic Line — Free
A single projection tells you what happens if returns are average every year. They never are.
Run your retirement plan against 5,000 randomized market scenarios — some with a crash in year one, some with a decade of strong returns, most somewhere in between. What comes back isn't a chart that goes up and to the right. It's a number: the percentage of those 5,000 outcomes where your money actually lasted.
Your plan survives in some percentage of 5,000 simulated outcomes — an actual number you can act on, not a single hopeful line on a chart.
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Sequence-of-returns risk, modeled properly
A market crash in your first year of retirement does far more damage than the same crash a decade later, even with identical long-run averages. A one-line projection can't show you that. This can.
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Guaranteed income sits underneath
State pensions and DB pensions form a floor beneath the simulation. Only the portfolio drawdown gets stress-tested against market variance, because guaranteed income doesn't move with the market.
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Nothing to sign up for
No account, no email required to see your numbers. Your financial data never leaves your browser.
What "84% Success" Actually Means
The number isn't a prediction. It's a description of how your specific plan — your accounts, your spending, your pension start dates — held up across 5,000 different possible market histories. An 84% score means 4,200 of those histories ended with money still in the pot. The other 800 didn't. That's the honest range a single projection line was always hiding.
The biggest single lever most people miss: delaying retirement by one or two years usually moves this number more than any portfolio tweak. Guaranteed income — deferring a state pension, adding rental income — helps too, because it reduces how much the simulation depends on the market at all.
Free, With No Trial Clock Running
No credit card at signup, because there's no signup. No 14-day trial that quietly becomes a subscription. No results locked behind a paywall after you've already entered your numbers. RetireFlexi is free because it started as a personal project — the founder needed exactly this and built it for himself first.
No Account, No Data on a Server
Everything you enter — account balances, pension estimates, income targets — stays in your browser on your device. There's no RetireFlexi database of retirement plans, so there's nothing to breach. If you save a plan, it's emailed to your own inbox as an attachment; RetireFlexi never reads or stores what's in it.
Common questions before you start
What is Monte Carlo simulation, in plain terms?
Instead of assuming your investments grow at the same rate every single year, the calculator runs 5,000 randomized market scenarios — some with strong early returns, some with crashes, some with a prolonged downturn right when you retire. The result is a percentage: your plan survives in, say, 84% of those 5,000 outcomes. That's a probability, not a guarantee.
Why does a single projection line lie to you?
A single projection assumes the same average return every year, which never actually happens. Sequence-of-returns risk means a crash in your first few retirement years does far more damage than the same crash a decade in, even if the long-run average is identical. A one-line projection hides that entirely.
Does this work with pensions and Social Security, not just investments?
Yes. State pensions, defined benefit pensions, and any other guaranteed income are modeled as a floor underneath the simulation — only the portfolio drawdown portion is stress-tested against market variance.
Is my financial information private?
Completely. Everything you enter stays in your browser on your device — nothing is sent to a server.
Is it actually free?
Free, with no paid tier at all and no account required to use it.
See Your Real Odds in About Five Minutes
Enter your accounts and income, and get a probability instead of a guess — free, and nothing you enter leaves your device.
Not financial advice. This calculator is a planning tool, not personalized investment advice. Monte Carlo simulation models a range of possible market outcomes based on historical volatility assumptions — it does not predict actual future returns. Consult a qualified financial adviser before making investment or retirement decisions.