Every asset card in your portfolio follows a set of simulation rules. Below you'll find exactly how each asset type behaves month-by-month — so you can build scenarios with confidence, not guesswork.
🏡
Home
Your largest asset deserves the sharpest model. The simulator tracks your home's market value month over month, applying your chosen annual return rate as steady appreciation (or depreciation). When it's time to sell, the engine handles the tax math so you don't have to.
Rule 1Your home's value compounds monthly at 1/12 of the annual return rate, giving you a realistic appreciation curve over time.
Rule 2Property tax is calculated using the annual tax rate you set, deducted monthly, and tracked as a separate expense metric so you can see exactly where your money goes.
Rule 3When you sell, capital gains are computed against your cost basis — with the $250K primary residence exclusion applied automatically if you've owned for 24+ months.
🏦
Mortgage
A proper amortization schedule — not a rough estimate. Enter your remaining balance, rate, and months left (check your statement), and the simulator builds your payment plan down to the penny.
Rule 1Monthly payments are calculated using the standard amortization formula, splitting each payment into principal and interest so you can watch your equity grow.
Rule 2The simulator tracks your months remaining and automatically closes the mortgage when the balance reaches zero — no manual cleanup needed.
Rule 3Mortgage interest is tracked as a deductible expense, giving you visibility into one of your largest annual tax write-offs.
💰
Monthly Salary
Income is the engine of your financial plan. The simulator credits your paycheck on the first of the month and handles withholding, so what flows into your accounts is the real take-home number.
Rule 1Your gross income is credited on day 1 of each month. At year-end, 1/12 of the annual return rate is applied as a raise — compounding your earning power year over year.
Rule 2FICA and Medicare are withheld automatically from each paycheck, so fund transfers downstream reflect your actual net income — not your gross.
Rule 3Estimated federal income tax withholding is computed from your filing status and tax bracket, keeping your simulation aligned with real-world payroll.
📉
Monthly Expense
Bills don't stay flat — and neither does your simulation. Expenses grow with inflation so you can stress-test whether your plan holds up in 10, 20, or 30 years.
Rule 1Expenses are debited at the end of each month, after all income and transfers have settled — mirroring how bills work in real life.
Rule 2Starting from month two, 1/12 of the annual return rate is applied at the beginning of each month as inflation — your $500 grocery bill today won't be $500 in a decade.
Rule 3Unlike salary (which compounds yearly), expense inflation compounds monthly — a subtle but meaningful difference over long horizons.
🏛️✨
Retirement Accounts
401(k) · IRA · Roth
Three flavors, one goal. Whether you're deferring taxes now, paying them later, or never — the simulator enforces IRS contribution limits and withdrawal rules so your projections stay realistic.
Rule 1Annual contribution limits are enforced: $23,500 for 401(k) ($31,000 if 50+) and $7,000 for IRA/Roth ($8,000 if 50+). Contributions are sourced from linked income via fund transfers.
Rule 2Required Minimum Distributions kick in at age 73 for tax-deferred accounts (IRA, 401k). The simulator uses the IRS Uniform Lifetime Table to calculate your annual RMD automatically.
Rule 3Tax treatment follows real-world rules: 401(k) and IRA withdrawals are taxed as ordinary income, while Roth distributions are tax-free — a powerful lever in your retirement planning.
📊
Brokerage Account
Your taxable investment account — flexible, liquid, and tax-aware. The simulator tracks your cost basis and holding period so capital gains are classified correctly when you withdraw.
Rule 1Growth compounds monthly at 1/12 of the annual return rate. Your cost basis is tracked separately, so gains are always measured against what you actually invested.
Rule 2On withdrawal, basis is reduced proportionally — not dollar-for-dollar — so your realized gain reflects the correct share of appreciation.
Rule 3Capital gains are classified as long-term (held 12+ months) or short-term, each taxed at their respective rates — because timing matters.
💵
Cash
In your wallet, your checking account, or under the mattress. Cash is king for liquidity — but unless you're in a deflationary spiral, it's your worst-performing asset class over time.
Rule 1If you assign an annual return rate, interest accrues monthly and is treated as ordinary income for tax purposes.
Rule 2No cost basis is tracked — every dollar withdrawn is a dollar, making cash the simplest asset type in the simulator.
Rule 3Cash is the default destination for fund transfers and acts as your portfolio's liquidity buffer between income and expenses.
🐖
Savings
High-yield savings accounts and certificates of deposit. A safe harbor for your emergency fund or short-term goals, with predictable returns and no market risk.
Rule 1Interest accrues monthly at 1/12 of the annual return rate and is classified as ordinary income.
Rule 2Behaves identically to cash in terms of tax treatment, but gives you a dedicated card to model different rates for different buckets of safe money.
💳
Debt
Credit cards, auto loans, student debt — anything with a balance and a rate. You set the payoff timeline, and the simulator builds the amortization schedule around it.
Rule 1Uses the same amortization formula as a mortgage, splitting each payment into principal and interest based on your rate and payoff period.
Rule 2You control the months-to-payoff — want to see what happens if you pay off that credit card in 12 months instead of 36? Change one number.
Rule 3The asset automatically closes when the balance hits zero, freeing up cash flow for the rest of your portfolio.
🇺🇸
US Treasury
Bills, notes, and bonds backed by the full faith and credit of the United States government. The benchmark for risk-free returns — and a cornerstone of conservative portfolios.
Rule 1Interest income accrues monthly via the annual return rate and is taxed as ordinary income at the federal level.
Rule 2The principal value stays flat — no price appreciation or depreciation is modeled, keeping the simulation focused on coupon income.
Rule 3Interest income flows into your annual tax computation, so you can see how treasuries affect your overall bracket and liability.
🏢
Corporate Bond
Higher coupons, higher risk. Corporate bonds let you model the yield premium you earn for lending to companies instead of the government — and the simulator treats the income accordingly.
Rule 1Interest accrues monthly at 1/12 of the annual return rate, just like treasuries — but typically at a higher coupon to reflect credit risk.
Rule 2All coupon income is taxed as ordinary income — no preferential capital gains treatment here.
Rule 3Like treasuries, no price appreciation is modeled — the focus is on predictable income, not speculative gains.
Fund Transfers
Money doesn't sit still — it flows. Fund transfers let you wire a percentage of one asset's value into another on a schedule you control. Pair your salary with your 401(k), your brokerage with your cash reserves, or set up a one-time sweep when an asset closes.
Recurring Transfers
Choose a frequency — monthly, quarterly, half-yearly, or yearly — and a percentage of the source asset's value to move each period.
On-Close Transfers
When an asset reaches its finish date, a separate close percentage sweeps the remaining value into the target account automatically.
Tax Rates
The IRS is the source of truth — and so is this simulator. 2024 brackets for Single and Married Filing Jointly are built in. Here are the publications we reference:
The income that kicks in when the paychecks stop. Model Social Security benefits or any recurring income stream that starts at a future date — so your retirement projections don't pretend you're living on air.
Rule 1Income is credited monthly starting on the asset's start date — perfect for modeling a Social Security benefit that begins at 62, 67, or 70.
Rule 2An optional annual return rate applies cost-of-living adjustments (COLA) at year-end, so your benefit keeps pace with inflation over a 30-year retirement.
Rule 3Retirement income is taxed as ordinary income and flows through the same withholding pipeline as salary — brackets, FICA exemptions, and all.
🏛️
Pension
FERS · CSRS · Military · State/Local
Model defined-benefit pension payments separately from Social Security. Pensions have their own COLA schedule and are kept distinct so future tax treatment differences (MAGI thresholds, the Social Security 85% rule) can be modeled accurately.
Rule 1Monthly pension income is credited starting on the asset's start date, just like Retirement Income.
Rule 2The annual return rate applies COLA adjustments (e.g. FERS 2% cap) — separate from Social Security COLA.
Rule 3Pension income is taxed as ordinary income but is exempt from FICA. No contributions or RMDs apply.
🔄
Life Events & Phases
Your financial life isn't one long straight line — it's a series of phases. During accumulation, your salary flows into 401(k)s and brokerage accounts. In retirement, the flow reverses: Social Security and retirement account drawdowns fund your living expenses. Life Events capture these transitions and automatically rewire your portfolio when each phase begins.
🟢 Accumulate Phase
The earning years. Income flows into savings, investments, and retirement accounts. Fund transfers route your salary to 401(k), Roth IRA, and brokerage based on the percentages you set for this phase.
🟠 Retire Phase
The drawdown years. Salary closes automatically. Social Security begins. Fund transfers flip: retirement accounts and brokerage now fund your living expenses — all configured independently from the accumulation phase.
Phase TransfersEach life event owns its own set of fund transfers. When you configure "Salary → 5% to 401(k)" in Accumulate and "401(k) → 40% to Living Expenses" in Retire, the simulator automatically switches between them at the transition age you set.
Asset ClosingLife events can close assets when a phase begins. When Retire triggers, Salary automatically closes — its on-close transfers fire, and the asset stops producing income. No manual intervention needed.
Color-Coded TimelineThe interactive timeline shows each phase as a colored segment — green for Accumulate, coral for Retire. Click any phase dot to jump to that date. The "You are Here" indicator, year/month selectors, and viewing badges all reflect the current phase's color.
Age-DrivenPhases are triggered by age, not fixed dates. Set your Current Age, Retirement Age, and Finish Age in the global settings, and the entire timeline — phase boundaries, asset start/end dates, and fund transfer activation — adapts automatically.
Why it mattersWithout phases, you'd need separate portfolios for "working" and "retired." Life Events let you model your entire financial arc — from first paycheck to last withdrawal — in a single simulation, with fund transfers that adapt to each chapter of your life.
Projections & Analysis
A single projection is a starting point — not the whole story. The simulator gives you five ways to interrogate your financial future, from a deterministic baseline to full stochastic analysis and AI-driven optimization.
📈 Value Projections
Your deterministic baseline — a line chart of any metric across every asset, month by month, for the full simulation horizon.
🎲 Monte Carlo
1,000 stochastic simulations with percentile bands. See below for the full story.
🛡️ Guardrails
Dynamic withdrawal rules that adapt spending to market reality. Details below.
📋 Spreadsheet
A detailed monthly data table across all metrics and assets — for when you want the raw numbers, not the chart.
🧾 Credit Memos
A complete audit trail of every transaction — every credit, debit, and transfer, with timestamps and descriptions.
📊 30+ Metrics
Track value, growth, income, dividends, capital gains, taxes, RMDs, contributions, distributions, cash flow, and more.
🎲
Monte Carlo Simulation
Your financial plan doesn't live in a world of fixed returns — so why should your projections? Monte Carlo simulation runs your portfolio through 1,000 randomized trials, each drawing from real historical market data, to show you the range of outcomes your plan might actually produce.
Correlated Year Sampling
Each trial picks a single historical year for all asset classes — S&P 500, treasury yields, CPI, and wage growth move together, preserving the real-world correlations that matter.
Percentile Bands
Results are summarized as 10th, 25th, 50th, 75th, and 90th percentile envelopes, with your deterministic baseline overlaid — so you can see the best case, the worst case, and everything in between.
Optional Guardrails
Toggle "With Guardrails" to re-run all 1,000 simulations with dynamic withdrawal adjustments active — and see how adaptive spending changes the shape of your outcomes.
Historical Data Foundation
Draws from the same FRED dataset as backtesting (1970–2025), so every random trial is grounded in decades of actual economic history — not fabricated distributions.
Why it mattersA single projection tells you what happens if everything goes exactly as planned. Monte Carlo tells you how likely that plan is to survive — and what to expect when it doesn't.
🛡️
Guyton-Klinger Guardrails
The 4% rule is a starting point — not a strategy. Guyton-Klinger guardrails give your retirement withdrawals an adaptive immune system: when markets drop, spending tightens automatically; when markets soar, you get a raise. The result is a plan that bends with reality instead of breaking against it.
Initial Withdrawal Rate
Your starting withdrawal as a percentage of portfolio value. This sets the baseline — guardrails adjust it from here.
Preservation Band
If your current withdrawal rate drifts above the initial rate by this margin, spending is cut — protecting your portfolio from depletion in down markets.
Prosperity Band
If your current withdrawal rate drifts below the initial rate by this margin, spending increases — so you actually enjoy the upside when markets deliver.
Adjustment Amount
The percentage by which withdrawals are raised or lowered when a guardrail is triggered — controlling how aggressively the system responds.
Dual-axis chartThe guardrails projection plots portfolio value and withdrawal amounts on separate axes, with event markers showing exactly when and why each adjustment fired.
Per-scenarioGuardrail parameters are saved per portfolio scenario, so you can compare conservative vs. aggressive withdrawal strategies side by side.
🕰️
Historical Backtesting
What if you could run your portfolio through actual market history? Backtesting replaces your user-provided rates with real historical data and advances year by year through the simulation — so you can see how your plan would have performed from any starting year between 1970 and 2025.
S&P 500 Annual Returns
Applied to equity accounts — Brokerage, 401(k), IRA, and Roth IRA — so your investments track actual market performance.
10-Year Treasury Rates
Applied to US Treasury bonds, reflecting the real yield environment for each historical year.
CPI Inflation
Applied to monthly expenses, so your cost of living grows at the actual inflation rate — not a static estimate.
Nominal Wage Growth
Applied to monthly income, so your salary tracks real historical wage growth year over year.
NoteHistorical data covers 1970–2025, sourced from FRED (Federal Reserve Economic Data). Once the simulation advances past the available historical years, your user-provided rates automatically resume for the remainder of the projection.
🔮
Maximizer
Genetic Algorithm Optimizer
Stop guessing your fund transfer percentages and withdrawal parameters. The Maximizer uses a genetic algorithm — inspired by natural selection — to evolve the best combination of fund allocations and guardrail settings for your specific portfolio. It runs directly inside the Maximizer section, updating the chart in real time as it discovers better solutions.
Spending ↔ Terminal Value Selector
A row of discrete notches lets you set the optimization objective. All the way left maximizes lifetime cash flow (spending in retirement). All the way right maximizes ending portfolio value (wealth preservation). Pick any point in between for a blended goal.
Evolvable Guardrail Genes
The optimizer doesn't just tune fund transfers — it also evolves your guardrail parameters (withdrawal rate, preservation, prosperity, adjustment) within realistic ranges to find the sweet spot for your chosen objective.
Phase-Aware Optimization
The chromosome encodes fund transfers grouped by life event phase. Accumulate-phase allocations are evolved independently from retire-phase allocations, and only assets active during a phase are included — Social Security won't appear in accumulation genes.
Real-Time Chart Updates
Watch the portfolio projection chart update live as the optimizer discovers better solutions. The generation counter, fitness status, and best terminal value are displayed below the chart throughout the run.
Real-World Constraints
A truly useful optimizer can't just chase math — it has to respect reality. The Maximizer enforces three tiers of constraints so its recommendations are actionable, not theoretical.
🔒 Immutable Transfers
Real Estate, Mortgage, and Debt fund transfers are locked to their original values. You can't optimize away your mortgage payment — it's a contractual obligation.
🔏 Partially Mutable
Monthly Expenses can vary ±25% of their original allocation. You can tighten the belt, but you can't eliminate groceries.
✅ Fully Mutable
All other transfers (salary routing, retirement account contributions, Social Security allocation) can be freely optimized from 0% to 100%.
Contribution CapsDuring accumulation, no more than 25% of income can flow to retirement accounts (401(k), IRA, Roth). In retirement, the cap drops to 10%. This prevents the optimizer from producing unrealistic over-contributions.
Debt PenaltyAny individual asset that ends with a negative balance incurs a fitness penalty proportional to the debt. This prevents the optimizer from concentrating losses in one account while inflating others.
Volatility PenaltyPortfolios that trigger frequent preservation cuts (guardrail spending reductions) are penalized — because a plan that constantly slashes your income isn't really a plan.
Recommendations
When the optimizer completes, click Recommendations to see a detailed comparison of your current fund transfers and guardrail settings versus the optimizer's best solution — organized by phase, with exact percentage changes for every transfer.
How it worksA population of 50 candidate portfolios competes over 200 generations. Each candidate encodes fund transfer percentages for every phase plus four guardrail parameters. The fittest survive, crossover, and mutate — converging on an allocation that respects real-world constraints while maximizing your chosen objective. The entire process runs in a Web Worker so the UI stays responsive.
⚡
AI Summaries
Every section of the simulator has a floating ⚡ button that generates a structured markdown summary of your portfolio's current state — ready to paste into a conversation with your financial advisor, an AI assistant, or your own notes. Each summary is tailored to its section and includes directional notes pointing to related insights elsewhere in the tool.
📅 Timeline Summary
Life event phases, trigger ages, fund transfer configurations per phase, and which assets close at each transition.
💼 Portfolio Summary
Every asset with starting value, ending value, asset type, annual return rate, and fund transfer routing.
📈 Projections Summary
Metric snapshots at key dates — start, retirement, and finish — with per-asset breakdowns and growth trends.
🎲 Monte Carlo Summary
Percentile ending values (10th through 90th), baseline comparison, and 10th–90th spread with warnings if the downside is negative.
🛡 Guardrails Summary
Current guardrail parameters and a table of every preservation cut or prosperity raise that fired during the simulation, with the year and adjusted rate.
📋 Details Summary
Credit memo audit totals per asset, lifetime tax summary (income, FICA, Medicare, capital gains, property), and annual cash flow table.
Why it mattersFinancial data is only useful if you can communicate it. Each summary is structured markdown — tables, headers, and bullet points — designed to be pasted into ChatGPT, Claude, an email to your advisor, or a planning document. Copy with one click.
Scenarios & Sharing
One plan is never enough. The simulator lets you build multiple scenarios — different retirement dates, different allocation strategies, different assumptions — and compare them instantly. When you're ready, share your entire portfolio with a single link.
Multiple Scenarios
Create parallel scenarios with different assumptions — each with its own assets, fund transfers, and guardrail parameters — and switch between them with a dropdown.
Instant Sharing
Compress your entire portfolio into a URL and share it via email. The recipient loads your exact scenario — assets, transfers, settings, and guardrails — in one click.
Auto-Persistence
Every change is automatically saved to your browser's local storage. Close the tab, come back tomorrow — your portfolio is exactly where you left it.
Portfolio Ledger
A real-time summary showing opening value, closing value, and CAGR (Compound Annual Growth Rate) across any metric — so you can benchmark performance at a glance.