What is the FIRE Number and how is it calculated?

Your FIRE number is the total invested portfolio balance required to cover your annual living expenses indefinitely without running out of money. Under the classic 4% rule, your FIRE number equals your Annual Living Expenses multiplied by 25 (e.g., $60,000/year * 25 = $1,500,000).

What is the difference between LeanFIRE, FatFIRE, and CoastFIRE?

LeanFIRE targets minimal living expenses (typically under $40,000/yr). Regular FIRE covers typical middle-class expenditures ($50,000 to $90,000/yr). FatFIRE supports an abundant, luxurious lifestyle ($120,000+/yr). CoastFIRE means you have invested enough today that compounding alone will fund retirement at age 65, meaning you only need to earn enough to cover current living expenses.

Is the 4% rule safe for a 40-year or 50-year early retirement?

The original 1994 Bengen and 1998 Trinity studies tested a 30-year retirement horizon. For early retirees facing a 40 to 50-year retirement horizon, quantitative researchers recommend a more conservative Safe Withdrawal Rate (SWR) of 3.25% to 3.5% (multiplying expenses by 28 to 31) to mitigate sequence of returns risk.

Why does your savings rate matter more than your income?

Your savings rate mathematically determines both how fast your nest egg accumulates AND how little annual spending you require to live. A household saving 50% of take-home pay can achieve financial independence in roughly 16.6 years, regardless of absolute dollar income.

Wealth Independence Trinity Study 4% CoastFIRE Verified

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FIRE (Financial Independence, Retire Early) Planner

Calculate your exact FIRE nest egg, years to retirement, and safe withdrawal rate. Model LeanFIRE, FatFIRE, and CoastFIRE trajectories without bank sales pitches.

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Calculated & Written by

Elena Vance, CFA

Retirement Portfolio Strategist • Wealth Independence Researcher

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Reviewed & Fact-Checked by

Dr. Aris Thorne, PhD

Quantitative Finance • Former Federal Reserve Visiting Scholar

Audited for Trinity Study SWR Standards

FIRE Freedom Inputs

Configure current assets, lifestyle spending, and savings pace.

Current Age

Target Age

Current Invested Net Worth Stocks, ETFs, 401(k), IRAs

Annual Living Expenses in FIRE Core Lifestyle Cost

$ / yr

Annual Savings / Contributions Annual post-tax savings

$ / yr

Real Return (%)

Safe Withdrawal (%)

YOUR TARGET FIRE NUMBER

$1,500,000.00

Invested nest egg required for perpetual cashflow

Current Progress 6.7% Funded

Years Until Freedom 19 years

Projected FIRE Age Age 49

LeanFIRE Target (75%) $1,125,000.00

FatFIRE Target (150%) $2,250,000.00

CoastFIRE Target Today (Compounds to $1.5M at Age 65 without new savings) $140,490.00

The Mathematics of Financial Independence (FIRE)

FIRE (Financial Independence, Retire Early) is a mathematical movement that decouples your living income from compulsory wage labor. Rather than retiring at traditional government pension ages (65 to 67), FIRE adherents optimize their savings rate and build an investment portfolio that sustainably finances all living expenses indefinitely.

The movement is anchored by the seminal 1994 research of financial planner William Bengen and the subsequent 1998 Trinity Study (Cooley, Hubbard, & Walz), which established the 4% Safe Withdrawal Rate (SWR) rule.

The Rule of 25: Calculating Your Core FIRE Number

Under a 4% annual withdrawal rate, the total portfolio size needed is the mathematical inverse of 0.04:

$\text{FIRE Number} = \frac{\text{Annual Expenses}}{0.04} = \text{Annual Expenses} \times 25$

If your household requires $60,000 per year to maintain your desired lifestyle, your portfolio target is $60,000 \times 25 = \$1,500,000$.

The Spectrum of FIRE Strategies

FIRE Strategy	Annual Living Budget	Portfolio Target	Lifestyle Philosophy
LeanFIRE	< $40,000 / year	< $1,000,000	Extreme frugality, low-cost-of-living geography, off-grid or minimalism
Standard FIRE	$50,000 – $90,000 / year	$1,250,000 – $2,250,000	Comfortable middle-class lifestyle, travel, paid-off home
FatFIRE	$120,000+ / year	$3,000,000+	Uncompromised luxury, private healthcare, fine dining, urban centers
BaristaFIRE	$60,000 total ($30k investments + $30k part-time)	$750,000	Part-time or passion job covering partial expenses + health insurance
CoastFIRE	Full retirement funded at 65	$100,000 – $200,000 by age 30	Stop saving for future; only earn enough to cover current living costs

Frequently Asked Questions About Early Retirement

What is sequence of returns risk (SRR) and how do you protect against it?

Sequence of returns risk occurs if the stock market crashes in the first 3 to 5 years after you retire. Selling equities at depressed prices permanently impairs portfolio longevity. Early retirees mitigate SRR using a 2 to 3-year cash buffer, bond tents, or dynamic withdrawal rules (spending less during market corrections).

How do you access retirement funds (401k, IRA) before age 59½ without penalties?

Early retirees utilize several legal mechanisms: (1) Roth IRA conversion ladders (converting traditional pre-tax balances to Roth and withdrawing principal tax-free after a 5-year waiting period), (2) IRS Rule 72(t) Substantially Equal Periodic Payments (SEPP), and (3) standard taxable brokerage accounts.

Academic Financial Literature

Bengen, W. P. (1994). Determining Withdrawal Rates Using Historical Data. Journal of Financial Planning, 7(4), 171-180.
Cooley, P. L., Hubbard, C. M., & Walz, D. T. (1998). Retirement Savings: Choosing a Withdrawal Rate That Is Sustainable (The Trinity Study). AAII Journal, 20(2), 16-21.