🎯 Risk-Based Guardrail Withdrawal Calculator

Monte Carlo Probability of Success Analysis

Based on the Risk-Based Guardrails methodology

📊 Input Parameters

Personal Information
Leave empty for single-person planning
Use younger spouse's age if couple
Portfolio Information
Asset Allocation

Total: 100.0%

Fees & Inflation
Enter as percentage (e.g., 0.75 for 0.75%, not 75)
Enter as percentage (e.g., 2.5 for 2.5%)
Income Sources (Social Security, Pensions, etc.)
Future Expenses
Spending Profile
Spending smile reflects research showing spending naturally declines in retirement
Guardrail Settings
When guardrails are breached, spending is adjusted to return to the target PoS

Why Enhanced Monte Carlo? Standard Monte Carlo assumes each year's return is independent. However, research by Kitces, Fitzpatrick & Tharp shows that this can overstate sustainable spending by 5–10% at typical confidence levels (70–90% probability of success), because real markets exhibit mean reversion — prolonged downturns are historically followed by recoveries, and vice versa.

Enhanced mode runs a second simulation using log-normal returns with mean reversion and displays both results side-by-side for comparison.

Runs a second simulation with mean-reverting returns alongside the standard one
-0.10
Autocorrelation coefficient (φ). More negative = stronger mean reversion. Default -0.10 is a conservative empirical estimate. Set to 0 for log-normal returns with no mean reversion.

Running Monte Carlo simulation...

📈 Analysis Results

📊 Standard vs. Enhanced Monte Carlo Comparison

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Probability of Success
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Desired Spending
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Recommended Spending
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Adjustment Needed
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Current Withdrawal Rate
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Enhanced Monte Carlo (Mean-Reverting)

Enhanced PoS
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Enhanced Recommended Spending
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Enhanced Adjustment
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Mean Reversion (φ)
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💡 Interpretation

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Portfolio Projection (Monte Carlo)

Income & Expenses Over Time

📊 Detailed Statistics

Monte Carlo Iterations: --
Successful Scenarios: --
Failed Scenarios: --
Median Final Portfolio: --
10th Percentile: --
90th Percentile: --
Expected Return: --
Portfolio Volatility: --
Current Year Income: --
Current Year Expenses: --
Current Year Withdrawal: --
Calculation Time: --

Enhanced Monte Carlo Statistics

Enhanced Iterations: --
Enhanced Successful: --
Enhanced Failed: --
Enhanced Median Final: --
Enhanced 10th Percentile: --
Enhanced 90th Percentile: --
Enhanced Calc Time: --

Disclaimer: This calculator is for educational and planning purposes only. It does not constitute financial advice. Monte Carlo simulations are based on historical return assumptions and may not predict actual future performance. Consult with a qualified financial advisor before making investment decisions.

Learn More About Risk-Based Guardrails