Monte Carlo Retirement Simulator
Run 2,000 simulated market futures to see the real chance your retirement money lasts, not just one average answer.
Why simulate instead of using one average return?
A normal retirement calculator assumes the market earns the same return every year. Real markets do not. A bad run of returns in the first few years of retirement, called sequence risk, can empty a portfolio even when the long-run average looks fine. This simulator draws 2,000 random sets of yearly returns around your average and counts how many futures survive.
How to read the result
The big number is the share of simulated futures where your money lasted the whole period. Many planners aim for 85% to 90% or more. The table shows a bad future (10th percentile), a median future and a good future (90th percentile) so you can see the range, not just the middle.
What it assumes
Spending rises with inflation each year and is taken at the start of the year. Returns follow a log-normal pattern. Stocks have historically had volatility near 15% to 18%, a balanced portfolio near 9% to 12%. Results use a fixed random seed, so the same inputs always show the same answer. This is an estimate, not advice.
Worked example
Last reviewed November 2026. Formulas are standard and shown in the sections above; results are estimates.
Tips and common mistakes
- Test a lower first-year spending to see how fast the odds improve.
- Use a lower return than the past average to be cautious.
- Add pensions or Social Security by reducing the spending you need from the portfolio.
Learn more
Frequently asked questions
What is a good success rate?
Many planners look for 85% to 90% or higher, and plan to adjust spending if markets fall. 100% is not realistic.
Why does the result not change when I reload?
The simulation uses a fixed seed based on your inputs, so the same inputs give the same answer.
Does it include taxes?
No. Enter spending after allowing for tax, or use the after-tax figure you need.
What is volatility?
How much yearly returns swing around the average. Higher volatility lowers the chance the money lasts.
Is this the same as the 4% rule?
The 4% rule is based on past US data. This tool lets you test your own return, risk, time and spending.
Money guides for this topic
All guides →When to Claim Social Security: 62, 67 or 70?
How claiming age changes your monthly check, what the break-even age means, and how to compare options with your own numbers.
Read guide →Will My Retirement Money Last? Understanding the Odds
Why a fixed 4% rule is only a starting point, what sequence-of-returns risk is, and how simulations show the chance of success.
Read guide →Investing for Beginners: A Simple Plan with the Numbers
A plain-English starter plan for investing: low-cost index funds, regular contributions and why fees matter.
Read guide →Related calculators
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Open calculator →Results are estimates and not financial advice.