How much do you need to retire? The 4% rule explained

"How much is enough?" has a famous shorthand answer — the 4% rule — and like most shorthand it is useful precisely as long as you remember what it leaves out. This guide explains where the rule comes from, how to use its 25x cousin for a quick target, and which real-world details should adjust the number before you trust it.

The 10-second answer

A common starting point: you need roughly 25 times the annual spending your savings must cover. That is the 4% rule rearranged — withdrawing 4% of the starting balance, adjusted for inflation each year, has historically lasted about 30 years. Spending $60,000 a year from savings implies a target near $1.5 million; spending $40,000 implies $1 million. Treat it as a first estimate, not a finish line.

Where the 4% rule comes from

The rule traces to a 1994 study by financial planner William Bengen, who back-tested withdrawal rates against US market history for portfolios of stocks and bonds. He found that an initial 4% withdrawal, raised by inflation every year afterward, survived every historical 30-year retirement in the data — including ones that began just before the Great Depression. Later work, including the well-known Trinity study, broadly confirmed the figure. The key detail people miss: 4% was the worst-case survivor, not an average. Many historical retirees could have spent more; the rule is built around the unlucky ones.

The 25x rule of thumb

Dividing by 4% is the same as multiplying by 25, which makes the rule easy to run in your head. The crucial subtlety is that the multiple applies to spending your savings must cover, not total spending. If you plan to spend $70,000 a year and expect $25,000 of reliable income from elsewhere, the gap is $45,000 and the 25x target is about $1.125 million — not $1.75 million. Getting the gap right matters more than any refinement to the multiplier.

What the rule ignores

The 4% rule assumes a 30-year retirement, so retiring at 50 or planning to 95 argues for a lower withdrawal rate and a bigger multiple. It was built on US historical returns, which may flatter the future, and it ignores investment fees — a 1% annual fee meaningfully lowers the safe rate, a drag explored in Fees, inflation, and returns. It also assumes you mechanically raise spending by inflation every year regardless of markets, when real retirees typically cut back in bad years, and it says nothing about taxes, healthcare shocks, or the particular misfortune of bad returns in the first few years of retirement.

Adjusting for pensions and Social Security

Reliable income streams shrink the savings problem dollar for dollar. A pension, an annuity, or Social Security reduces the spending gap your portfolio must fill, and because the gap gets multiplied by 25, every $1,000 of dependable annual income lowers the savings target by roughly $25,000. Timing matters too: benefits that start at 67 or 70 leave early-retirement years fully funded by savings, which is why a single multiple can misstate plans with staggered income. A year-by-year projection handles this better than any rule of thumb.

Turn the rule of thumb into a projection

The retirement calculator replaces the 25x shortcut with an explicit year-by-year model: savings grow with contributions until retirement, then spending — inflated annually and offset by other income — draws the balance down to your planning age. If a workplace plan is your main savings vehicle, estimate its contribution with the 401(k) calculator first, then test whether the combined plan survives a planning age of 90 or 95.