Free Monte Carlo Retirement Simulator
Set your portfolio, your contributions and how you plan to draw it down. The simulator plays that plan forward 1,000 times, each run with its own sequence of market returns and inflation, and shows you the whole range of outcomes rather than one number pretending to be a forecast. No signup, and nothing you enter is stored.
Retirement Simulator
Quick simulation with preset portfolios
Running simulation…
How to read these results
Every run of this simulator plays your plan forward 1,000 times. Each run draws its own random sequence of annual returns and inflation, so no two runs are alike. What you get back is a distribution of outcomes, not a forecast — the point is to see how wide the range is and where your plan starts to break, not to find a single number.
- The blue line is the median: half of all runs finished above it, half below.
- The blue band holds the middle 50% of runs for each year.
- The gray band holds 80% of runs. One run in ten finished above it, one in ten below.
- The success rate is the share of runs that paid for every withdrawal in full, all the way to the end.
Rather be shown than told?
The guided tour walks through the chart, the success rate and the withdrawal distribution on your own results, pointing at each one as it goes. Run a simulation first and the tour will cover the result panels too.
What the success rate leaves out
The headline number tells you how often a plan survived. It does not tell you when the failures happened, and that usually matters more. A plan that succeeds 90% of the time with failures arriving at age 92 is a very different plan from one that also succeeds 90% of the time with failures arriving at 74. The first is a risk you could absorb by trimming spending late; the second breaks while you still have decades to fund.
The engine records the year of the first withdrawal it could not fully fund, for every run that fails. That turns a single pass/fail number into a distribution of depletion dates. When the success rate drops below 100%, the red area on the chart shows exactly when and how often portfolios ran dry — once you have run a simulation.
What the presets assume
The free simulator models a single holding. Each preset is a nominal expected return and an annual volatility — both before inflation, and both editable. If you have your own assumptions, override them.
| Preset | Expected return | Volatility |
|---|---|---|
| S&P 500 | 10% | 15% |
| World ETF (default) | 7% | 13% |
| Government Bonds | 3% | 5% |
The expected return you set is the rate the portfolio actually compounds at over the run. Inflation is modelled separately, with its own average and volatility, so purchasing power erodes at a different rate in every run. The horizon runs to age 95.
The two withdrawal strategies
Both are available in the free simulator, and switching between them on identical inputs is the quickest way to see what a withdrawal strategy actually buys you.
Classic — the “4% rule” style
Your withdrawal is fixed at retirement — your chosen percentage of the portfolio at that moment — and then rises with inflation every year afterwards, regardless of what markets do. Spending is completely predictable. The portfolio absorbs all of the risk.
Guyton-Klinger guardrails
Starts identically, then reacts. Inflation raises are skipped in years the portfolio lost ground. If your withdrawal drifts more than a set band above the rate you started with, spending is cut; if it drifts the same distance below, spending rises. You absorb some of the risk so the portfolio does not have to.
Guardrails almost always improve the success rate. They are not free: they buy that survival with variable income. Switch the withdrawal chart to its real view and watch what happens to spending in the worst runs — that variability is the actual price, and it is the number to judge the strategy on.
What this simulator does not model
Worth knowing before you read too much into a result. None of the following is included:
- Taxes and account types. Nothing distinguishes taxable accounts from tax-deferred or tax-free ones, and there are no mandatory distribution rules.
- State pension or social security. Model it approximately by lowering your withdrawal rate, or by treating the pension as income you simply do not draw.
- Longevity. The horizon is fixed and every result is conditional on living to the end of it. This is not a life-expectancy calculation.
- Healthcare and long-term care costs, which for many plans are the largest single risk.
- Fees. Subtract your expected costs from the return assumption yourself.
- Multiple assets. The free tier models one holding, so there is no allocation, no rebalancing, and no correlation between assets.
Historical return series and the regime-switching model — which simulate crisis, inflationary and stable-growth market states with correlated assets — are part of Personal Edition.
Questions about this simulator
What do the percentile bands actually mean?
They describe the spread of the 1,000 runs at each year, not a confidence interval around a prediction. The blue band contains the middle half of runs and the gray band contains 80% of them, so one run in ten ended above the gray band and one in ten below it. No individual run follows a band — each one is a jagged path, and the bands are just where those paths cluster. .
Does a 95% success rate mean my plan is safe?
Not on its own. It means 5% of runs ran out of money before the horizon ended, and it says nothing about when. Check the red failure area on the chart: failures concentrated in your late eighties are a different problem from failures starting in your seventies. Chasing 100% usually costs more in foregone spending than the risk is worth — flexibility in bad years tends to be worth more than a higher headline number.
Why does one percentage point of return change the outcome so much?
Because it compounds. Over a thirty-year horizon a single point of annual return moves the median outcome far more than most people expect, and the effect is larger again once withdrawals are running against the portfolio at the same time. This is the main reason to treat any single result as one point in a range: run your plan at a return a point or two lower and see whether the conclusion still holds.
What return and volatility should I use?
The presets are long-run nominal figures before inflation and before costs: 10% return with 15% volatility for the S&P 500, 7% with 13% for a World ETF, 3% with 5% for government bonds. Subtract your own fund costs. If you want to see how sensitive your plan is, the more useful exercise is running the same plan at a return one or two points lower rather than trying to find the correct number.
Guardrails or a fixed withdrawal?
Guardrails raise the success rate by cutting spending after bad years and raising it after good ones. Whether that is a good trade depends on how much of your spending is genuinely flexible. If most of your budget is fixed costs, a strategy that can cut your income by 10% is offering a survival rate you cannot actually collect on. Run both on identical inputs and compare the real withdrawal chart, not just the success rate.
Is my data stored anywhere?
No. The free simulator requires no account, and the values you enter are sent to the simulation engine to compute a result and are not saved to a profile. To share a setup, run it and use the Share link button under the results — it copies a link with your inputs written into it, so the settings travel in the URL rather than sitting on a server.
This tool provides statistical simulations based on historical data and modeled assumptions. Results are not predictions or guarantees of future performance. This is not financial advice. The creators accept no liability for decisions made based on these simulations. Please seek professional financial advice before making investment decisions.