Simulated Market Volatility
Each simulation generates random annual returns based on historical market behavior. Some years gain 20%, others lose 15%. The calculator models this variability across 100-1,000 scenarios.
Probabilistic Modeling
Free Monte Carlo Retirement Calculator
Will your money last through retirement? Run hundreds of market simulations to find out. See your probability of success, best case, worst case, and percentile outcomes — all free, no signup.
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Monte Carlo Results
Monte Carlo in plain English
Traditional retirement calculators assume a fixed return every year. Reality is messier. Monte Carlo simulations model that messiness to give you a realistic picture.
See the Range of Outcomes
View the 10th, 25th, 50th, 75th, and 90th percentile outcomes on an interactive chart. Understand your worst case, median, and best case scenarios at a glance.
Probability of Success
See what percentage of simulations ended with money remaining. 90% means 9 out of 10 market scenarios supported your withdrawal plan through retirement.
Why Monte Carlo?
Better than a single projection
A fixed 7% return assumption ignores the reality that returns vary wildly year to year. Monte Carlo shows you what could happen, not just what might happen on average.
Real Market Behavior
Markets don't return 7% every year. Some years surge, others crash. Monte Carlo captures this randomness using Gaussian distribution.
Stress Test Your Plan
See how your retirement holds up in the worst 10% of scenarios, not just the median. Plan for adversity, not just average outcomes.
Adjust and Re-Run
Change your withdrawal rate, starting balance, or timeline and re-run the simulation instantly. See how small changes affect your success rate.
FAQ
Monte Carlo questions
A Monte Carlo simulation runs hundreds or thousands of retirement scenarios with randomized market returns. Instead of assuming a fixed 7% annual return, it models the reality that some years gain 20% and others lose 15%. The result is a probability of success rather than a single projection.
My Projection Calculator runs 100 to 1,000 iterations. Each iteration generates random annual returns based on historical market volatility using the Box-Muller transform for Gaussian distribution. You can see the 10th, 25th, 50th, 75th, and 90th percentile outcomes on the results chart.
The probability of success shows what percentage of simulations ended with money remaining at your target date. For example, 90% success means that in 90 out of 100 simulated market scenarios, your portfolio lasted through retirement. Most planners consider 80-90% success rates acceptable.
Yes, completely free with no account required. Enter your assets, set your withdrawal rate, and run the simulation instantly. Your data stays in your browser, and you can export results or share via a unique link.
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Learn MoreRun your Monte Carlo simulation
See your probability of retirement success across hundreds of market scenarios. Free, no signup.
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