The 4% Rule Explained

Where the 4% rule came from

Financial planner Bill Bengen coined it in 1994 after testing every 30-year retirement period in U.S. market history back to 1926. He found that a 50/50 stock/bond portfolio could survive every one of those periods at a 4% withdrawal rate.

The famous 'Trinity Study' (1998) confirmed Bengen's work and made the rule famous. Both relied on historical U.S. market data, which has been kinder than most global markets.

How to actually apply it

1. On day one of retirement, calculate 4% of your portfolio (e.g., $1M × 4% = $40,000).
2. Withdraw that $40,000 over year one.
3. Each subsequent year, increase the dollar amount by inflation (not 4% of the new portfolio value).
4. Continue until age 95 or you run out — whichever comes first.

What the math actually shows

Across every rolling 30-year period since 1926, the 4% rule survived in roughly 96% of scenarios. The few failures involved retiring at the worst possible time (1929, 1966) — i.e., right before a major bear market.

In most scenarios, the retiree actually ENDED with more money than they started. The 4% rule is conservative — it's built to survive the worst case, not the average case.

Modern critiques and adjustments

Lower rate for early retirees

A 30-year rule doesn't work for someone retiring at 50 with a 45-year horizon. Use 3.25%–3.5% for very early retirees.

Higher rate with flexibility

Bengen himself now suggests 4.7% may be safe if you're willing to cut spending temporarily during bear markets. The 'guardrails' approach lets you withdraw more in good years and less in bad ones.

International data is worse

Studies using global market data (Japan, UK, etc.) suggest 3.0%–3.5% is safer than 4% for portfolios not 100% in U.S. stocks.

What 4% means for your retirement number

Flip the 4% rule and you get the 25× rule: multiply your desired annual spending by 25 to find your retirement target.

• Spend $30K/year → need $750K
• Spend $50K/year → need $1.25M
• Spend $75K/year → need $1.875M
• Spend $100K/year → need $2.5M

What different withdrawal rates require

Dropping from 4% to 3% raises the target by a third — which is why retiring at 50 is a fundamentally harder problem than retiring at 65.

Worked example: a 30-year retirement

A $1,200,000 portfolio, 60/40 stocks and bonds, first-year withdrawal of $48,000 indexed to inflation:

• Year 10 withdrawal at 2.5% inflation: about $61,400
• A poor first decade of returns is the main failure mode — sequence risk, not average return
• Trimming withdrawals by 10% during down years historically pushes success rates well above 95%

Test your own figures in the retirement income calculator and the FIRE calculator.

Related questions

Does the 4% rule still work?

As a planning heuristic, yes. As a promise, no — it was derived from a 30-year US horizon and a specific asset mix. Longer retirements argue for 3.3–3.5%.

Should I adjust withdrawals for market performance?

Flexible rules — skipping the inflation increase after a down year — improve survival more than any asset allocation tweak.

Where does Social Security fit?

It reduces the portfolio's job. Subtract expected benefits from annual spending before multiplying by 25 — see how much money do you need to retire.

Key takeaways

• The 4% rule implies a target of roughly 25× annual spending.
• Sequence of returns matters more than average returns in the first decade.
• Longer retirements justify a more conservative 3.3–3.5% rate.
• Guaranteed income sources reduce the portfolio you need to build.

Use the calculator