Understanding RetireNumber
Transparent tools for transparent planning. Learn how we calculate your retirement projections, where our data comes from and the methodology behind our simulations.
Start with the calculator
Read the guides, then run your plan with the free retirement number calculator and full retirement timeline tool.
Nobel Prize-Winning Data
Our historical data comes from Robert Shiller, the economist who won the Nobel Prize for his work on asset prices.
95+ Years of History
Test your retirement plan against every market condition since 1928, including the Great Depression, stagflation, dot-com bust and 2008 crisis.
Transparent Methodology
Every calculation is documented. We explain exactly how we project your portfolio and what assumptions we make.
Documentation Guides
How RetireNumber Works
Start herePlain-English overview: what the tool does, what you enter and what you get back in 60 seconds.
Historical Data Sources
EssentialLearn about Robert Shiller's Nobel Prize-winning dataset that powers our backtesting, 95+ years of market data since 1928.
Methodology
The math behind projections, Monte Carlo simulations, withdrawal rates and default assumptions.
Limitations
What the model can and can't know: assumptions, boundaries and when to get professional advice.
Understanding Backtesting
What backtesting is, its benefits and limitations and why it's a powerful tool for retirement planning.
Withdrawal Strategies
PopularCompare different withdrawal methods: from the classic 4% Rule to dynamic CAPE-based strategies.
Glossary of Terms
Definitions of key retirement and investment terms, from CAPE ratio to sequence of returns risk.
Retirement Concepts
Retirement Number
What is a retirement number, how to calculate yours and why a single figure isn't enough.
When Can I Retire?
The four variables that determine your retirement date and what moves the needle most.
Safe Withdrawal Rate
The 4% rule, where it came from, when it breaks and the alternatives.
Sequence Risk
Why the order of returns matters more than average returns, and how to protect yourself.
Social Security
How benefits are calculated, when to claim and how it affects your retirement number.
Taxes in Retirement
How different accounts are taxed, why your bill can be higher than expected and strategies to reduce it.
Roth Conversions
When to convert, how much and the trade-offs between paying tax now vs later.
Withdrawal Order
Which accounts to draw from first and how to optimize your lifetime tax bill.
FIRE and Its Variants
Six different targets for the same idea. Each one trades money against years differently, and the right one depends on your budget rather than on which label sounds best.
What is FIRE?
Financial Independence, Retire Early. The target, the savings rate and what the arithmetic leaves out.
Coast FIRE
The balance that reaches your target with no further saving. The earliest milestone worth hitting.
Barista FIRE
Portfolio covers most of your spending, part-time work covers the rest. Often chosen for the insurance.
Lean FIRE
Full independence on a small budget. Fastest to reach and the least forgiving if anything changes.
Chubby FIRE
The middle ground. Comfortable rather than frugal, without the Fat FIRE timeline.
Fat FIRE
Independence without cutting your standard of living. Costs more years than people expect.
Important Disclaimer
RetireNumber does not provide financial advice. The projections and simulations are for educational and planning purposes only. Past performance does not guarantee future results. Please consult a licensed financial professional before making financial decisions.