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30+ FIRE terms defined simply — bookmark this page for reference
The FIRE community has its own language. Your first Reddit thread might feel like reading a foreign dialect — SWR, LeanFIRE, 72(t), OMY, SEPP. Once you learn the vocabulary, the concepts click into place quickly. This glossary covers every term you will encounter on the path to financial independence, organized by category.
The Core Numbers
Financial Independence (FI)
The point at which your investment portfolio generates enough passive income to cover your living expenses indefinitely — without you needing to work. FI is the "F" in FIRE. Many people reach FI and keep working by choice; others stop immediately. The key is that work becomes optional.
FIRE Number (FI Number)
The portfolio size you need to be financially independent. Calculated as: Annual Expenses × 25. If you spend $50,000 per year, your FIRE number is $1,250,000. Also called your "FI target" or simply "the number." Every dollar you cut from annual spending reduces your FIRE number by $25.
Safe Withdrawal Rate (SWR)
The percentage of your portfolio you can withdraw each year without running out of money over a long retirement. The most widely cited SWR is 4%, derived from the Trinity Study. For early retirees with 40–50 year horizons, many use 3.25%–3.5% to be more conservative.
The 4% Rule
A retirement planning guideline stating that withdrawing 4% of your portfolio in year one, then adjusting for inflation each year, has historically lasted 30+ years in virtually all market conditions. It is the mathematical basis for the "multiply by 25" FIRE number formula. Based on the 1994 Trinity Study.
Savings Rate
The percentage of your take-home income you invest each month. Calculated as: Monthly Savings ÷ Monthly Take-Home Income × 100. A 10% savings rate leads to FIRE in ~43 years. A 50% savings rate gets you there in ~17 years. Your savings rate is the most powerful variable in your FIRE timeline — more impactful than investment returns or income level.
Net Worth
Your total assets minus your total liabilities. Assets include investment accounts, home equity, savings, and any other owned property of value. Liabilities include mortgages, car loans, student debt, and credit card balances. Net worth is the primary metric FIRE practitioners track monthly to measure progress.
FIRE Variants
Lean FIRE
Retiring on a lean budget — typically under $40,000 per year for a single person or couple. Lean FIRE requires a smaller portfolio (often under $1 million) but demands strict spending discipline and geographic flexibility. Popular with minimalists and those willing to live frugally for permanent freedom.
Fat FIRE
Retiring with a generous lifestyle budget — often $80,000–$150,000+ per year. Fat FIRE requires a larger portfolio ($2–4 million) but gives maximum lifestyle flexibility with no spending constraints. Typically pursued by high earners who do not want to compromise their standard of living in retirement.
Coast FIRE
Saving aggressively early until your portfolio is large enough to grow to your FIRE number on its own — without adding another dollar. At that point you "coast": you can stop investing and just cover living expenses with current income. Example: if your FIRE number is $1.5M and you have $400,000 at age 35, compound growth alone will get you there by 65 even if you add nothing more.
Barista FIRE
Semi-retiring with part-time work that covers basic living expenses while your investment portfolio continues to grow toward full FI. Named after the idea of taking a low-stress job (like a café barista) that provides health insurance and spending money. You are not fully FI, but you are done with stressful high-income careers.
Flamingo FIRE
A structured two-phase approach: save until you reach half your FIRE number (50%), then semi-retire or take lower-stress work while compound growth does the rest. Like a flamingo that stands on one leg — half the work, full the eventual outcome. It lets you escape the corporate grind years before reaching full FI.
Slow FIRE
Pursuing financial independence at a relaxed pace without extreme frugality or sacrifice. Slow FIRE accepts a longer timeline (15–25 years) in exchange for maintaining a comfortable lifestyle throughout the journey. No side hustles required, no extreme budget cuts — just consistent, moderate saving over time.
Chubby FIRE
The middle ground between regular FIRE and Fat FIRE. Typically defined as retiring with a $2–3 million portfolio and spending $80,000–$120,000 per year. Allows for comfortable travel, dining out, and lifestyle spending without requiring the extreme income or extreme frugality of other paths.
Investment Terms
Index Fund
A mutual fund or ETF that tracks a market index (like the S&P 500) by holding all — or a representative sample — of the stocks in that index. Index funds are the investment vehicle of choice for the FIRE community because they have very low fees, require no stock-picking skill, and historically outperform most actively managed funds over long time periods.
Expense Ratio
The annual fee charged by a mutual fund or ETF, expressed as a percentage of your investment. A 0.04% expense ratio on $100,000 costs you $40 per year. A 1.0% ratio costs $1,000. Over 30 years, a 1% fee difference on a $500,000 portfolio can cost you over $300,000 in lost compound growth. FIRE practitioners aim for expense ratios under 0.10%.
Asset Allocation
How you divide your portfolio between different asset classes — typically stocks and bonds. A common early-stage FIRE allocation is 90% stocks / 10% bonds, shifting toward 70/30 or 60/40 as you approach or enter retirement. Asset allocation determines both your expected return and your portfolio volatility.
Dollar-Cost Averaging (DCA)
Investing a fixed amount at regular intervals (such as every paycheck) regardless of market conditions. DCA automatically buys more shares when prices are low and fewer when prices are high. It removes the temptation to time the market and is the default behavior of most 401(k) contributions.
Sequence of Returns Risk
The danger that a major market downturn in the early years of retirement will permanently damage your portfolio — even if long-term average returns are fine. Selling depressed assets to fund living expenses locks in losses before the market recovers. Managing sequence risk is one of the most critical challenges for early retirees.
Account Types & Tax Strategy
401(k)
An employer-sponsored retirement account with a 2026 contribution limit of $24,500 ($32,500 if 50+). Traditional 401(k) contributions are pre-tax (reduce taxable income now; taxed on withdrawal). Roth 401(k) contributions are after-tax (no deduction now; tax-free in retirement). Funds cannot be accessed penalty-free until age 59½ — unless you use the Rule of 55 or SEPP.
Roth IRA
An individual retirement account funded with after-tax dollars. Contributions grow tax-free and withdrawals in retirement are completely tax-free. Contribution limit: $7,500/year (2026). Crucially, contributions (not earnings) can be withdrawn at any age without penalty — making it a key tool for early retirees. Income limits apply for direct contributions.
HSA (Health Savings Account)
A tax-advantaged account available to those on a high-deductible health plan. Contributions are pre-tax, growth is tax-free, and withdrawals for medical expenses are tax-free — a triple tax advantage unmatched by any other account. After age 65, funds can be withdrawn for any purpose (taxed like a traditional IRA). The FIRE community often treats the HSA as a "stealth IRA."
Bridge Fund
A taxable brokerage account (or other liquid savings) used to fund living expenses in early retirement — before you can access tax-advantaged accounts penalty-free at 59½. Because most retirement savings are locked in 401(k)s until 59½, early retirees need a bridge to cover the gap between retirement age and 59½. Typically 8–15 years of expenses.
Roth Conversion Ladder
A strategy for accessing traditional IRA or 401(k) money before age 59½ without penalties. You convert a portion of your traditional account to a Roth IRA each year, pay income tax on the conversion, then withdraw the converted amount five years later — tax and penalty free. Requires 5-year advance planning before you retire.
SEPP / Rule 72(t)
Substantially Equal Periodic Payments — an IRS provision allowing penalty-free withdrawals from a 401(k) or IRA before age 59½, as long as you commit to a fixed withdrawal schedule for at least 5 years or until age 59½, whichever is longer. Complex to implement; consult a CPA before using.
Rule of 55
An IRS provision that allows penalty-free withdrawals from a 401(k) if you leave your employer in or after the year you turn 55. Applies only to the 401(k) of the employer you just left — not IRAs or old employer 401(k)s. A useful bridge for those retiring in their mid-50s.
FIRE Culture Terms
One More Year Syndrome (OMY)
The psychological trap of delaying retirement indefinitely — always deciding to work "just one more year" to build a bigger cushion. OMY is extremely common among people who have already reached their FIRE number but struggle with the identity shift or fear of leaving a secure income. Recognizing it is the first step to overcoming it.
F.U. Money
Enough savings to walk away from any job, client, or situation you dislike — without financial panic. F.U. money does not necessarily mean full financial independence; it means enough of a cushion that you have genuine options and leverage in your career. Often the first milestone people aim for before full FI.
Monte Carlo Simulation
A statistical method that runs thousands of randomized market scenarios to estimate the probability your portfolio survives a given retirement horizon. Instead of assuming average returns, Monte Carlo accounts for variability and sequence risk. A 90% success rate means your portfolio survived in 900 of 1,000 simulated scenarios. MyFIRE's planner includes a Monte Carlo engine.
Trinity Study
A landmark 1994 academic study by three professors at Trinity University that analyzed historical portfolio survival rates across different withdrawal rates and asset allocations. Found that a 4% withdrawal rate from a stock/bond portfolio had near-perfect historical survival over 30-year periods. The source of the 4% rule that underpins all FIRE math.
Tip
You do not need to master every term before starting. Learn FI Number, Savings Rate, and Bridge Fund first — those three concepts drive 80% of the decisions you will make on your FIRE journey. Come back to this glossary when you encounter an unfamiliar term.
Legal disclaimer
This article is for educational purposes only and does not constitute financial advice. MyFIRE is not a registered investment advisor. Always consult a qualified fee-only CFP before making retirement or investment decisions.
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