The 4% rule is the cornerstone of retirement planning: if you withdraw 4% of your portfolio annually, your savings should last 30+ years. Here's the full picture.
The Origin Financial planner William Bengen studied historical market returns in 1994 and found that a portfolio of 50-75% stocks could sustain 4% annual withdrawals for at least 30 years in virtually every historical scenario, including the Great Depression and 1970s stagflation.
The Math - Desired annual retirement income: $60,000 - Required portfolio: $60,000 / 0.04 = $1,500,000 - Or more simply: 25x your annual expenses
Limitations and Refinements 1. Sequence of returns risk: retiring in a bear market can derail even sound plans 2. 30-year horizon: if retiring at 55, you need a 40-year horizon — some researchers suggest 3.3% for early retirees 3. Inflation: the original study assumed inflation-adjusted withdrawals 4. Social Security reduces your required portfolio — subtract SS income from your target spending first
A More Robust Approach Plan for 3.5% withdrawals to add safety margin, keep 1-2 years of expenses in cash to avoid selling in downturns, and be willing to cut discretionary spending 10-15% in bad market years. Flexibility is the key variable the 4% rule doesn't capture.
Action Step Calculate your "financial independence number": multiply your desired annual expenses (after Social Security) by 25. That's your target portfolio size.