4% Rule vs Trinity Study Update 2027 Calculator
Trinity Study (1998): 4% withdrawal rate from 50/50 stock/bond portfolio = 95% success for 30 years. Modern updates (Bengen 2024, Kitces 2025) suggest: 4% remains safe for 30 yrs but 50-yr retirement (FIRE) needs 3.0-3.3%. Dynamic methods (guardrails, VPW) increase safe rate to 4.5-5%.
Trinity Study 1998
Originally tested 1926-1995 data. 4% inflation-adjusted withdrawal from 50/50 portfolio = 95% success for 30 yrs. Updated annually since.
Bengen 2024 Update
With international diversification + small-cap value tilt, SWR rises to 4.5%. Pure US large-cap, drops to 3.7%.
Dynamic Withdrawal
Guardrails (Guyton-Klinger 2006): cut spend 10% if portfolio drops 20%. VPW (Bogleheads): recalculate annually. Higher initial rate, more flexibility.
Source and Disclaimer
Trinity 1998, Bengen JFP 2024, Kitces.com Nerd's Eye View. Past performance doesn't guarantee future safety.
Source: Trinity Study 1998, Bengen JFP. Last updated: May 2026.