Enough

Alternative to Trinity Study's safe withdrawal calculator

The Trinity Study: the research behind the 4% rule.

In 1998, three Trinity University professors published the paper that validated Bengen's 4% rule across multiple asset allocations. It's the single most-cited piece of retirement research. Here's what they actually concluded — and what you should do with it.

Assumed return

7.0%

Withdrawal rate

4.0%

Savings rate

—

landmark 1998 withdrawal-rate research paper

What Trinity Study's Numbers Mean For You

Using Trinity Study's assumed 4.0% withdrawal and 7.0% return. "Years to FI" assumes a $50,000 starting portfolio and $2,000/month contributions.

Annual SpendingFIRE # (Trinity Study)FIRE # (4% rule)Years to FI
$40,000$1,000,000$1,000,00017.9y
$70,000$1,750,000$1,750,00024.4y
$120,000$3,000,000$3,000,00031.3y

The Methodology

Cooley, Hubbard, and Walz (Trinity University, 1998) tested fixed-percentage withdrawal rates against every rolling 15-, 20-, 25-, and 30-year period between 1926 and 1995. They found that a 50/50 or 75/25 stock/bond portfolio withdrawing 4% (inflation-adjusted) succeeded in 95-100% of historical 30-year periods. 5% dropped to 83% success; 6% to 68%. An updated 2011 version extended the data through 2009 and confirmed the result. This is the empirical foundation for the '4% rule.'

Citations

  • “4% withdrawal rate 95-100% success over 30-year periods” — Cooley, Hubbard, Walz (1998), AAII Journal
  • “50/50 or 75/25 portfolio tested” — Trinity Study original paper, Table 3
  • “1998 original, 2011 update through 2009” — Cooley, Hubbard, Walz (2011), 'Portfolio Success Rates'

Our Honest Take

Where Trinity Study is right

The Trinity Study is real science. Its conclusions are robust across multiple portfolio compositions, time periods, and sensitivity analyses. If retirement planning has a canonical reference, this is it.

Where we differ

The Trinity Study tested 30-year retirements. For a 45-year-old who retires today and lives to 95, that's a 50-year horizon. Published extensions (Pfau, Kitces) show the safe rate drops to ~3.25-3.5% at that horizon. Our SWR Calculator uses horizon-adjusted rates by default.

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Where You Retire Changes Your Number

Trinity Study'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 Trinity Study's publicly stated retirement methodology. It is not officially endorsed by or affiliated with Trinity Study or their organization. Retirement planning involves significant uncertainty — consult a qualified fiduciary advisor before acting on any calculation.