Most free retirement calculators give you a single projected number. Retirfi gives you a probability distribution because that's how retirement actually works.
The standard retirement calculator asks for your expected rate of return and spits back a number. It might say "you'll have $1.4 million at 65." What it doesn't tell you is that this assumes markets behave exactly as expected, every single year, for 30+ years. They won't.
Monte Carlo simulation has been the standard in institutional financial planning for decades. Your financial advisor's software almost certainly uses it. But free tools for individuals almost never offer it, or if they do, they strip out all the complexity that makes it useful.
Retirfi brings professional-grade simulation to anyone with a browser.
When you click Run, Retirfi simulates hundreds of possible futures for your portfolio. Each run uses randomized market returns drawn from historical volatility distributions, some runs get unlucky sequences, some get lucky ones. Most land somewhere in between.
The result isn't "you'll have $X." It's "in 87% of 1,000 simulated futures, your money outlasts you." That's a fundamentally more honest answer.
Each simulation year draws a return from a normal distribution calibrated to historical equity and bond volatility. Cash accounts use near-zero volatility. The engine runs 200–1,000 paths (your choice) and tracks portfolio balance, withdrawals, and account types across all paths simultaneously.
In retirement, the order you withdraw from accounts matters enormously for lifetime tax liability. Retirfi follows the academically-supported optimal order: taxable brokerage → cash/HYSA → traditional (pre-tax) → Roth (last resort). Traditional withdrawals are modeled as ordinary income; brokerage as long-term capital gains. Required Minimum Distributions are forced from traditional accounts starting at age 73 or 75 per SECURE 2.0.
Retirfi estimates your Primary Insurance Amount (PIA) using SSA's bend point formula on your estimated Average Indexed Monthly Earnings (AIME). Spousal benefits are calculated per SSA rules, the spouse receives the higher of their own earned benefit or 50% of the primary earner's PIA, adjusted for early claiming. All benefits are indexed for COLA inflation annually in retirement.
Mortgages, car loans, and student debt are amortized month-by-month. As balances pay off, the freed cash flow can be allocated to investment contributions or treated as spending, your choice. Escrow costs (taxes + insurance) are modeled separately with their own inflation rate.
Retirfi stores your plan in your browser's localStorage. Nothing is sent to our servers unless you voluntarily enter your email to save a cloud backup. We don't sell data, run targeted ads based on your financial information, or share anything with third parties.
Advertising on this site is served by Google AdSense, which uses cookies for ad personalization. You can opt out via Google's ad settings.
Retirfi is for educational and planning purposes only. It is not financial advice. The simulation uses simplified models. It does not account for every tax nuance, doesn't model state taxes in detail, and it uses historical volatility that may not reflect future markets.
Results are projections, not guarantees. Please consult a licensed financial advisor (CFP, CFA, or RIA) before making major retirement planning decisions.
Run your first Monte Carlo simulation in under 5 minutes. No account required.
Open the Calculator →