How Much Do You Need to Retire? The 4% Rule Explained

The 4% rule is the most influential framework in retirement planning. It answers the most important retirement question — how much do I need? — with a single elegant calculation. The rule states that if you withdraw 4% of your portfolio in the first year of retirement and adjust that dollar amount for inflation annually, your portfolio has historically survived 30+ years in virtually every historical market scenario.

The Math

The 25× multiplier is simply the inverse of 4%. These are planning targets, not guarantees — your specific number depends on retirement age, health care costs, expected longevity, portfolio composition, and other income sources.

The Research Behind It

Financial planner William Bengen introduced the 4% guideline in 1994, studying US market returns from 1926 onward. He found that a 60/40 stock/bond portfolio withdrawing 4% annually, adjusted for inflation, never depleted within any 30-year historical period — including the Great Depression and the 1970s stagflation era. The Trinity Study (1998) extended and confirmed the research.

The Caveats That Matter

The original research used US-only portfolios and historically above-average US returns. For early retirees needing 40–50 year portfolio longevity rather than 30 years, many planners now suggest 3.5% (28× multiplier) as more conservative. In any case, these are starting-point guidelines — not guarantees — and flexible spending in down market years significantly improves outcomes.

Sequence of returns risk is the single biggest threat: a severe market downturn in the first five years of retirement, combined with ongoing withdrawals, can permanently impair a portfolio even when markets eventually recover. Holding 1–2 years of expenses in cash or short-term bonds reduces this risk by giving the invested portfolio time to recover without being drawn down at depressed prices.

Social Security Changes the Calculation

The 4% rule applies to the income your portfolio must generate — not your total spending. Social Security reduces what the portfolio must provide, which meaningfully reduces the required portfolio size. If you need $70,000/year in total income and will receive $22,000/year from Social Security, your portfolio only needs to generate $48,000/year — requiring approximately $1,200,000 rather than $1,750,000. Model your specific situation carefully before concluding you are behind.

Progress Benchmarks

Fidelity's savings benchmarks help track progress toward a 4% retirement: 1× annual salary by 30, 3× by 40, 6× by 50, 8× by 60, 10× by retirement (assuming retirement around age 67). Falling behind these benchmarks is common and recoverable — raising your savings rate by even 3–5 percentage points in your 40s makes a substantial difference to the final number.