Trinity study calculator

The Trinity question — how often a fixed initial withdrawal lasts 30 years — run as 1,000 seeded paths you can edit. This is not a reprint of Cooley, Hubbard and Walz (1998).

The calculator

Year-one withdrawal$40,000
1,000-path success76%
10th percentile ending$0
Median ending$1,248,685

Not the 1998 tables

Trinity used overlapping historical 30-year windows on a 50/50 portfolio. This page uses Killion’s lognormal band (seed 20260828, 1,000 paths, 12% volatility as a 50/50 stand-in). The question is the same; the sample is not. For the study we actually ran, see is the 4% rule still safe.

Assumptions

Fixed real dollar withdrawals, start-of-year, no fees, no taxes. Volatility is 12% unless you treat the band as a sensitivity, not a forecast.

Frequently asked questions

What is a Trinity study calculator?
The 1998 Trinity study asked how often a fixed-percentage initial withdrawal lasted 30 years on overlapping historical windows. This page asks the same question on 1,000 seeded paths so you can change the rate, the spend and the horizon.
Is this a reproduction of Cooley, Hubbard and Walz 1998?
No. It is the same kind of question on Killion’s lognormal band, not their historical tables. The 4% research post is the paper we actually ran.
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