👤 Personal Information
Plan for longevity risk
💰 Current Employment Income
Expected annual increase
% of salary matched
🏛 Social Security
Enter your estimated monthly benefit from ssa.gov. The model adjusts for claiming age (reduced at 62, full at FRA, +8%/yr delayed to 70).
Full Retirement Age benefit
Annual cost-of-living adjustment
⚠️ Disability Scenario
Model a long-term disability event. Disability insurance typically pays ~60-67% of base salary, tax-free if you paid premiums with after-tax dollars. Contributions to 401k, ESPP, and other payroll deductions stop. SSDI may apply — benefits are based on your earnings record and automatically convert to retirement benefits at FRA.
Enable Disability Scenario
Age when disability begins
LTD typically pays 60-67%
Only if "Custom Age" selected
Annual ESPP amount that stops
When disability is enabled: Earned income is replaced by LTD payments. 403(b), 457(b), DCP, employer match, and ESPP all stop at disability start age. Salary raises stop. Withdrawals prioritize 457(b) first (no early penalty).
📋 SSDI (Social Security Disability)
If you qualify for SSDI, you receive benefits based on your earnings record. After 24 months on SSDI, you qualify for Medicare (regardless of age). At your Full Retirement Age, SSDI automatically converts to regular retirement benefits at the same amount — there is no early-claiming reduction. Your earnings record is frozen at disability onset, so your PIA is based on earnings up to that point.
Eligible for SSDI
0 = auto-estimate from FRA benefit
Standard: 5-month waiting period
📈 Unvested Stock / RSUs
Model unvested equity that vests on a schedule. On disability, no new grants are issued — only existing unvested shares continue to vest (if your plan allows). Enter the total unvested value and remaining vesting period.
💵 Other Income Streams
🏠 Primary Residence
California Prop 13: Assessed value can only increase by max 2% per year from the base year (purchase year). Tax rate is approximately 1% of assessed value plus local overrides, Mello-Roos, and special assessments.
Tracks CPI + local premium
County base rate (typically 1%)
Annual special assessments
Bonds, school levies, etc.
$7,000 assessed value reduction
Max 2% per year by law
💳 Mortgage
📈 Prop 13 Tax Projection
Updates live as you change values above
🏙 Home Maintenance & Insurance
% of home value per year
🚚 Downsizing / Sale Plan
Rent or new mortgage after sale
📊 Investment Accounts
Enter current balances. The model will track growth, contributions, and withdrawals across account types with different tax treatments.
📈 Portfolio Allocation
Set your target allocation. The model uses historical VFINX (S&P 500) returns for equities, Bloomberg Aggregate for bonds, and T-bills for cash.
60%
30%
10%
Glide path (reduce equities in retirement)
Years to shift from current to retirement allocation
💲 Contributions (Pre-Retirement)
403(b) and 457(b) have separate limits — you can max both. DCP contributions are employer-funded and vest on schedule. ESPP deductions stop on disability.
2025 limit: $23,500 (+$7,500 catch-up 50+)
Separate $23,500 limit (stacks!)
2025 limit: $7,000 (+$1,000 catch-up 50+)
11% of salary; IRS max $25k purchase/yr
Typical: 15% with lookback
2025 family limit: $8,300
Employer-funded deferred comp
💵 Withdrawal Strategy (Retirement)
Starting rate, adjusted by method
Cut spending above this rate
Increase spending below this rate
📊 Total Expenses
💰 Monthly Living Expenses
Enter your baseline monthly expenses. These inflate annually at the CPI rate. Housing costs are computed separately from the Housing tab.
📅 Annual Expenses
🔄 Recurring Purchases
Items bought on a cycle — "new phone every 3 years", "car every 8 years", "roof every 20 years", etc. All amounts inflate at CPI.
🔮 One-Time Future Expenses
Planned future events — wedding, college tuition, medical procedure, etc.
🩺 Healthcare
Historically ~5-6% annually
Parts B, D, and Medigap
📊 Expense Breakdown
🏢 Federal Tax Settings
2025 federal tax brackets are built in. Adjust assumptions below for projections.
2025 MFJ: ~$30,000
Annual bracket adjustment
Long-term capital gains rate
Roth Conversion Ladder Strategy
Fill up to this taxable income level
Years between retirement and SS/RMDs
🌞 California State Tax
2025 MFJ estimate
California taxes all income including capital gains as ordinary income. Top marginal rate: 13.3%.
📈 Tax Projection
✈ Relocation Scenario
Compare staying in your current home vs. moving to a different city or state. Relocation analysis runs alongside the main simulation when enabled.
📅 Move Timing
🏙 Destination
🏠 Housing Strategy
Agent fees, title, escrow (5-7% typical)
New Home Details
State median shown
Rental in Destination
Rental Income from Current Home
Your New Rental in Destination
💰 Financial Preview
Estimates based on current inputs. Run simulation for Monte Carlo results.
📈 Relocation vs. Stay Comparison
Run the main simulation with relocation enabled to see comparative results here.
🎲 Monte Carlo Parameters
0 = random, or fix for reproducibility
📈 Return Assumptions
Historical data bundled from VFINX (1976–2024) and FRED. You can override the assumptions below.
Historical VFINX: ~10.2%
Historical VFINX: ~15.5%
💥 Market Crash Modeling
Enable fat-tail modeling to capture severe drawdowns beyond normal distribution.
Enable crash modeling
~4% matches historical frequency
Average crash severity
Years of above-average returns after crash
Added to mean return during recovery
📈 Inflation Model
Consumer Price Index, historical mean ~3%
Personal Consumption Expenditures
📋 Historical Data Reference
Bundled data used as the basis for simulation parameters. Click to view.
📊 Run a Simulation
Configure your parameters in the other tabs, then click "Run Simulation" to see results. The Monte Carlo engine will generate thousands of scenarios and present probability distributions.
📈 Portfolio Value Over Time
Shaded regions show confidence intervals from Monte Carlo simulation.
🎲 Success Probability
--
Probability of not running out of money
💰 Terminal Wealth Distribution
💵 Annual Cash Flow (Median Scenario)
📈 Withdrawal Rate Over Time
💰 Income Sources Over Time (Median)
📊 Scenario Analysis
Median
Worst 5%
Best 5%
Custom
📄 Export Simulation Data
Export the full monthly simulation detail as CSV. Includes every income source, expense category, tax computation, portfolio balance by account type, and withdrawal amounts — one row per month per scenario.
🔒 Privacy First
Your financial data never leaves your browser. This application runs entirely client-side — there is no server, no database, no analytics, no tracking pixels, no cookies (other than localStorage on your own machine), and no network requests beyond loading Chart.js from a CDN. Your income, assets, expenses, and simulation results are yours alone.
All data you enter is stored in your browser's localStorage. It persists across page reloads but never leaves your device. If you clear your browser data or use the Reset button, it's gone — there is no backup on any server. You can verify this by opening your browser's Network tab: the only outbound request is the Chart.js library download.
📚 How It Works
This retirement planner uses Monte Carlo simulation to model thousands of possible futures for your finances. Rather than assuming a single average rate of return, it samples from historical market data and adds realistic variance, including fat-tail crash events with recovery dynamics.
The simulator models each month from your current age through the end of your planned retirement horizon. At each step it computes: employment or disability income, Social Security and SSDI benefits, stock vesting, account contributions (403(b), 457(b), DCP, ESPP, IRA, Roth, HSA, taxable), investment returns per asset class, federal and California state taxes, all expense categories, and portfolio withdrawals using a dynamic guardrail strategy.
Key modeling features include:
- Historical data — bundled VFINX returns (1976–2024), CPI-U, PCE deflator, and Bloomberg Aggregate bond returns from the St. Louis Fed (FRED)
- Prop 13 property tax — California's 2% annual cap on assessed value increases from your purchase year
- Disability scenario — LTD income, SSDI with 5-month waiting period, Medicare after 24 months, RSU vesting control
- Smart withdrawal ordering — 457(b) first (no early penalty), then DCP, taxable, traditional, HSA, and Roth last
- Tax engine — 2025 federal brackets (MFJ/Single) and California's 10-bracket system with mental health surcharge
- Crash modeling — configurable probability, severity, duration, and recovery dynamics with fat tails
💻 Source Code & License
This project is open source and available on GitHub:
github.com/phubbard/retirement-simulator
© 2026 Paul Hubbard. Built with care, a healthy dose of paranoia about financial data privacy, and Claude.