Enough

Alternative to Bill Bengen's 4% rule calculator

The actual 4% rule, from the man who invented it.

In 1994, financial advisor William Bengen published the paper that created the '4% rule.' Most people quote it wrong. Here's what Bengen actually found — and what he's revised his number to since.

Assumed return

7.0%

Withdrawal rate

4.8%

Savings rate

—

creator of the 4% safe withdrawal rule

What Bill Bengen's Numbers Mean For You

Using Bill Bengen's assumed 4.8% withdrawal and 7.0% return. "Years to FI" assumes a $50,000 starting portfolio and $2,000/month contributions.

Annual SpendingFIRE # (Bill Bengen)FIRE # (4% rule)Years to FI
$40,000$833,333$1,000,00015.9y
$70,000$1,458,333$1,750,00022.2y
$120,000$2,500,000$3,000,00028.9y

The Methodology

Bengen's 1994 Journal of Financial Planning paper studied rolling historical returns from 1926-1992. He found that a retiree withdrawing 4.15% of initial portfolio value, then adjusting that dollar amount for inflation each year, never ran out of money in any 30-year period — even retiring into the 1966 stagflation. The portfolio assumed 50-75% stocks, 25-50% bonds. Bengen has since revised the number upward: his 2020 update suggests 4.7-4.8% is achievable with a more diverse portfolio (adding small-cap value, international, and cash buckets).

Citations

  • “Original 4.15% SAFEMAX, 1926-1992 data” — Bengen (1994), Journal of Financial Planning, 'Determining Withdrawal Rates Using Historical Data'
  • “Revised 4.7% with more diverse portfolios” — Bengen interview, FA magazine 2020; interview with Michael Kitces
  • “50-75% stocks / 25-50% bonds optimal range” — Bengen (1994)

Our Honest Take

Where Bill Bengen is right

Bengen's research is the mathematical foundation of the FIRE movement. His data is still the gold standard for sequence-of-returns risk analysis.

Where we differ

For early retirees with 40+ year horizons, the 4% rule was not designed to answer that question. We run Monte Carlo simulations with horizon-adjusted rates (3.25-3.5% for 50-year horizons, per Wade Pfau's expansions). Our SWR calculator shows per-horizon rates, not a single number.

Try the Enough FIRE Calculator

Set your own return and withdrawal rate assumptions. Pick any city in the world to adjust your FIRE number for local cost of living.

Open FIRE CalculatorSafe Withdrawal Rate Tool

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Where You Retire Changes Your Number

Bill Bengen's math assumes a generic US cost of living. The state or country you retire in can move your FIRE number by 30-70%. Start with a tax-friendly state or an international destination:

Florida

No income tax

Texas

No income tax

Portugal

D7 + NHR

Thailand

Territorial

Browse all 50 US states → · International retirement guides →

This page is an independent educational analysis of Bill Bengen's publicly stated retirement methodology. It is not officially endorsed by or affiliated with Bill Bengen or their organization. Retirement planning involves significant uncertainty — consult a qualified fiduciary advisor before acting on any calculation.