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

The rule comes from research on historical US portfolios of stocks and bonds, usually credited to financial planner William Bengen in the 1990s and popularised by the so-called Trinity study. The finding: a retiree who withdrew 4% of their starting portfolio in the first year, then increased that dollar amount each year with inflation, would not have run out of money over any 30-year period in the historical data tested.

Notice what it is not: a guarantee, a law, or a rule for every country, every portfolio and every retirement length.

Dividing 1 by 4% gives 25. Spend $40,000 a year and you need $1,000,000; spend $60,000 and you need $1,500,000. Change the rate and the answer moves sharply:

Going from a 4% to a 3% withdrawal rate raises the required portfolio by a third. That is why the “right” rate is such an important choice. Try your own spending in the FIRE calculator, or plan the saving side with the retirement calculator.

The historical tests covered about 30 years. Someone retiring at 45 may need the money for 50 years, and a longer horizon needs a lower rate to survive the same bad luck. Many in the FIRE community therefore plan on 3–3.5%.

The chart below uses a simple, steady model — a 3% real return and a fixed inflation-adjusted withdrawal — to show the shape of the trade-off on a $1,000,000 portfolio:

Under these illustrative assumptions a 4% withdrawal lasts 40+ years, 5% lasts 30 years and 6% lasts 23 years. The point is not the exact years but how quickly the balance curves downward once withdrawals outpace growth.

Real markets do not deliver a smooth 3%. A big fall in the first few years of retirement hurts far more than the same fall later, because you are selling assets at low prices to fund spending and leave less to recover. Two retirees with the same average return can end up with very different outcomes depending on the order of good and bad years. Common defences include holding a cash buffer for a year or two of spending, being willing to cut spending in bad years, and starting with a lower withdrawal rate.

• Taxes: withdrawals from traditional accounts are taxable income, so spending needs may be lower than withdrawals.
• Other income: Social Security, a pension or part-time work reduce what the portfolio must fund.
• Fees: a 1% fund fee comes straight off your sustainable rate.
• Healthcare and long-term care: costs can rise sharply late in life.

Treat 4% as a starting point, not a verdict. Estimate your real spending, subtract guaranteed income, choose a withdrawal rate that fits your retirement length and risk tolerance, and review yearly. A flexible plan — spending a little less after poor market years — is more robust than any fixed rule. This article is educational, not financial advice; a qualified adviser can model your taxes and benefits.