Disclaimers & Methodology

Educational purposes only — not financial advice

These tools are provided for educational and illustrative purposes only. They are not financial, investment, tax, or legal advice. Results are estimates based on simplified models and should not be used as the basis for financial decisions. Consult a qualified financial professional before making any significant financial choices.

Your data stays on your device

We do not collect, store, or transmit any of your personal financial information to our servers. All data you enter is saved locally in your browser using localStorage to preserve your calculations between visits. For your privacy, avoid entering sensitive personal information such as full legal names, Social Security numbers, or account numbers.

How the planner calculates

Retirement number — Your savings target, calculated as 25× your annual expenses (the 4% rule). This is the point where a 4% annual withdrawal covers your costs indefinitely under average market conditions.

Debt payoff — A mortgage payment, and any other debt payment you enter, are treated as flat amounts that stop once the balance clears. Neither is adjusted for inflation, because a fixed payment does not rise with prices. Your projected spending steps down at each payoff. For non-mortgage debt we work out the payoff date ourselves from the balance, rate, and monthly payment; if the payment does not cover the interest, we tell you so and leave your spending flat rather than assume a payoff that never happens.

Why debt does not change your savings goal — Your retirement number stays 25× the spending you entered. A debt that clears in a few years is not part of the spending you will carry through retirement, so folding it into a lifetime target would overstate what you need. Debt affects the year-by-year projection, not the goal. If you tell us your monthly spending figure already includes the debt payment (the default), we treat that payment as part of what you already spend rather than adding it on top — otherwise the same dollars would be counted twice.

Range of Outcomes — Rather than a single projected path, the planner runs 500 simulated market scenarios using log-normal returns. The shaded band shows the middle 80% of possible outcomes; the line is the most likely path.

Today’s dollars — Every figure the planner shows you — projected balances, the chart, your retirement number, the age you reach it — is in today’s dollars, deflated at 3% annual inflation. A projected balance of $928,000 means it would buy what $928,000 buys now, not the larger number that would print on a statement. The spending and contribution amounts you enter are treated the same way: we assume you keep them level in today’s dollars, so a $10,000 annual contribution rises with inflation in nominal terms rather than quietly shrinking in real ones. Amounts that genuinely do not rise with prices — a fixed mortgage or debt payment, a pension without a cost-of-living adjustment — are held flat in nominal terms and therefore shrink year by year in today’s dollars, which is what actually happens to them.

Market scenarios — Three growth assumptions drive the simulation. Each percentage below is the median nominal return — the typical year, before inflation is taken out. It is also the rate the projection line compounds at, so the chart and the simulation describe the same portfolio rather than two slightly different ones. In today’s dollars a typical Base year is about 4.9% while working (8% growth less 3% inflation) and about 1.9% in retirement.

• Bear (conservative): 5% while working, 3% in retirement, 12% annual volatility
• Base (moderate): 8% while working, 5% in retirement, 10% annual volatility
• Bull (optimistic): 11% while working, 7% in retirement, 14% annual volatility

Social Security — Expected monthly benefits offset portfolio withdrawals from your chosen claiming age. Benefits are inflation-adjusted in the projection. Figures are self-reported — verify your actual estimate at ssa.gov.

Retirement trigger — Decumulation starts at your chosen retirement age, regardless of portfolio balance. The 25× number is a planning benchmark, not a trigger.

Simplifying assumptions

• Log-normal return distributions are an approximation. Real markets have fatter tails — crashes and booms can be more extreme than the model expects.
• Inflation is modeled at a flat 3% annually. Actual inflation varies.
• The 25× retirement number (4% rule) is a guideline, not a guarantee. It has held historically but may not in all future market environments.
• Taxes on withdrawals are not modeled. Distributions from 401(k)s, traditional IRAs, and taxable accounts are generally subject to income tax.
• Fees are not modeled. The 5% / 8% / 11% and 3% / 5% / 7% figures are gross returns — no expense ratio, advisory fee, platform fee, or trading cost has been deducted, and no fee drag is baked into them. Your own costs come straight off the top: a portfolio charging 0.50% a year turns a Base 8% into roughly 7.5% before inflation. To make the planner reflect what you actually pay, subtract your all-in expense ratio from the growth rate you enter.
• Contribution limits (401k, IRA), healthcare costs in retirement, and means-tested benefit reductions are not modeled.
• Debt payments are modeled as a flat amount that stops at payoff. We do not model minimum-payment schedules, promotional rates, rate changes on variable-rate debt, new borrowing, or the interest you would save by paying a balance down faster.
• Program rules (withdrawal ages, Social Security, etc.) can change; verify current rules for your situation.

How to use responsibly

1. Run all three market scenarios. Bear shows what happens if markets underperform; Bull shows the upside. The gap between them is your real uncertainty range.
2. Pay attention to the “Likelihood your money lasts to 100” percentage — a low number signals meaningful longevity risk even in the most likely path.
3. Use results to generate better questions for a financial professional, not as final answers.