Most free retirement calculators handle only a few variables and project one number. RetirFi lets you run multiple scenarios with multiple variables and gives you a probability distribution, because that is how the real world works.
So, a bit about me, why I built this Monte Carlo tool, and why it's free. For a variety of reasons, I will remain anonymous. Mainly, I'm still working, and I don't want this tool to affect my work with clients.
For the past 15 years, I've worked as a private wealth attorney at a large firm, where I've helped many families with wealth preservation and wealth transfer across their personal and commercial assets. I've worked with everyone from families worth hundreds of millions of dollars to the average Joe.
And honestly, working with the middle of the wealth spectrum is my favorite. The quiet millionaire with a house, a 401(k), investments, and savings. They're saving for retirement, building a college fund, and still going on decent vacations. I like working with these families because the advice is actually useful and makes a difference in their lives. They are the ones who truly benefit.
Over my career, I've served as trustee of many trusts, invested and managed trust assets, hired and fired advisors, and had to make the investment decisions myself. My favorite tool along the way has been the Monte Carlo simulator. Many financial advisors have access to it, but I've found it is a combination of art and science. It doesn't matter how great the tool is if it's not in the right hands. I've seen great advisors use it wonderfully, and I've seen advisors struggle to figure it out.
But in almost every case, it is quite expensive to use. Most fee-based plans cost anywhere from $3,000 to $5,000 per year. Other wealth shops will offer it for free if you keep a minimum of $1 million with them.
So that's when I decided to build my own. I couldn't stand to see these high prices. Great advice for only those who could afford it, when those who can't afford it need it the most. (I'm a big fan of free tools and software.)
Maybe one day I'll create a login portal, but for now I wanted this to be as easy and accessible as possible.
When you click Run, RetirFi simulates hundreds of possible futures for your balance sheet. Each run uses randomized market returns drawn from historical data. Some runs get unlucky sequences, some get lucky ones. Most land somewhere in between.
The result is not "you'll have $X" or "you need $X to hit your retirement goal." It is "in 87% of 1,000 simulated futures, your money doesn't run out." That is a more honest answer, because it puts a number on the uncertainty instead of hiding it.
None of the free calculators I've found online are comprehensive. They usually focus on just one asset. RetirFi lets you input multiple accounts, different return assumptions, different retirement dates, Social Security, spousal benefits, one-time future events like college expenses, and debt schedules.
It takes all of your assets and liabilities, income and expenses, and stress tests your balance sheet.
Each simulation year draws a return from a normal distribution calibrated to historical stock 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. You can adjust the inflation assumptions too.
Mortgages, car loans, and student debt are amortized month-by-month. As balances pay off, the freed-up 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.
The same primary sources recur across the site.
Errors get fixed, not buried. If a figure on the site is wrong or out of date, let me know through the contact page and I'll correct the article and revise its updated date.
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.
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RetirFi is for educational and planning purposes only. I'm an attorney, but I'm not your attorney, and nothing on this site is legal, tax, or investment 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.
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