The 4% Rule Explained

The 4% rule is a rule of thumb for how much you can safely withdraw from an investment portfolio in retirement without running out of money. In its original form it says: in your first year of retirement, withdraw 4% of your portfolio. Every year after that, withdraw the same dollar amount adjusted upward for inflation. Historically, a balanced stock-and-bond portfolio survived a 30-year retirement under this rule in almost every rolling period studied.

It is the foundation of the most popular shorthand in the FIRE community: the 25× rule. If 4% of your portfolio covers your expenses, then 25 × your annual expenses is the portfolio you need. Spend $40,000 a year → target $1,000,000 invested. You can sanity-check that target against your own numbers with the Financial Independence Target Calculator.

The 4% rule traces back to two pieces of research. In 1994, financial planner William Bengen published a paper analysing every 30-year rolling retirement period in US market history, testing how much a retiree could safely withdraw without depleting a portfolio of stocks and bonds. His historical test used portfolios combining common stocks and intermediate-term U.S. Treasury securities. With a 50/50 stock-and-bond mix, a 4% starting withdrawal adjusted for inflation lasted at least 30 years in every historical period he tested. Bengen also argued for equity allocations between 50% and 75%, with a preference toward the upper end of that range.

Source: Bengen (1994), “Determining Withdrawal Rates Using Historical Data”.

In 1998, three professors at Trinity University — Cooley, Hubbard, and Walz — formalised the analysis in what became known as the Trinity Study. They tested multiple portfolio mixes (100/0, 75/25, 50/50, 25/75, 0/100 stocks/bonds), multiple withdrawal rates, and multiple retirement lengths, reporting the historical "success rate" of each combination.

The Trinity Study reframed this historical testing in terms of portfolio success rates. For a 50/50 portfolio combining the S&P 500 with long-term corporate bonds, a 4% inflation- adjusted withdrawal survived 95% of the rolling historical 30-year periods tested. Results vary with the asset mix, bond series, time period and methodology.

In these historical tests, "success" means that the portfolio still had a positive balance at the end of the tested period. It does not mean that the starting principal was preserved, and a historical success rate is not the same as the probability that a retirement beginning today will succeed.

Source: Pfau (2015), “Sustainable Retirement Spending with Low Interest Rates: Updating the Trinity Study”.

The 4% rule spread for three reasons. First, it's simple. Multiply expenses by 25 and you have a target you can put on a Post-it. Second, it's empirical — it's backed by a century of actual market data, not a forecast. Third, it inverts cleanly. Anyone can compute their own "FIRE number" in under a minute.

For everyday savers it answers the question that almost nothing else in personal finance does: "How much is enough?" Without a number, retirement is a vague aspiration. With one, it's an engineering problem.

Precision matters here, because the rule is almost always misquoted. The original 4% rule has four specific assumptions:

• Starting withdrawal of 4% of the portfolio in year one — not 4% of the current balance every year.
• Inflation adjustments to the dollar amount each subsequent year (e.g. $40k becomes $41.2k after a 3% CPI year).
• A 30-year horizon, not 40, 50, or 60.
• A diversified portfolio of roughly 50–75% US stocks and 25–50% US bonds.

Change any of those — longer retirement, different country, heavily bond-weighted portfolio, dynamic withdrawals — and the rule's historical success rate shifts. Sometimes higher, often lower.

"I withdraw 4% of my balance every year"

That's a different strategy (a fixed-percentage rule), and it produces wildly variable income year to year. The original rule fixes the dollar amount and only adjusts for inflation.

"4% is guaranteed"

It isn't. It's a historical success rate, not a contract. Future returns, inflation regimes, and bond yields may differ. Treat 4% as a planning anchor, not a promise.

"It includes taxes"

It doesn't. The 4% comes out gross. Taxes on traditional 401(k) withdrawals, capital gains, and dividends are paid from inside that 4%, so always model expenses after tax.

"It works for any retirement length"

It was designed for 30 years. Longer horizons generally support a lower starting withdrawal rate, all else equal. In Morningstar's 2025 base-case analysis, the estimated starting rate fell from 3.9% at 30 years to 3.5% at 35 years and 3.3% at 40 years. Those are the results of one model under one set of assumptions, not an OVELDA recommendation and not a guarantee. The appropriate figure depends on the horizon, asset allocation, return assumptions, spending flexibility, fees and the methodology used.

Source: Morningstar (2025), “The State of Retirement Income: 2025”.

• Empirical. Built on real market data across bull markets, depressions, and stagflations.
• Simple. One number, no spreadsheet required to start planning.
• Historically durable across many 30-year periods. In Bengen's tests, a 4% starting rate often produced portfolio longevity well beyond the 30-year requirement.
• Universally understood. Acts as a common language across the FIRE community and most modern retirement planning tools.

• US-centric data. The 20th-century US is arguably the most successful equity market in history. Other countries' rates are often lower.
• Static withdrawal. Real retirees adjust spending. The rule assumes you don't, which is unrealistic.
• Ignores fees and taxes. Even a 0.5% fee drag materially affects long-run success.
• 30-year horizon. Inappropriate for someone retiring at 40 with a 50–60 year horizon.
• Sequence-of-returns risk. The rule's worst historical outcomes happened to retirees who started in bear markets — a risk you can't predict in advance.

Sequence-of-returns risk is one of the most important concepts in withdrawal planning. Two retirees can experience the same average return over 30 years and end up with wildly different outcomes — purely because of the order those returns arrive.

A worked example

Two retirees, Anna and Ben, each start with $1,000,000 and withdraw $40,000 at the end of each year. Their portfolios earn the same three annual returns — −15%, −15% and +20% — but in opposite order. To keep the arithmetic transparent, this illustration ignores inflation adjustments and runs for three years only.

• Anna gets the losses first: her balance falls to $810,000, then $648,500, then recovers to $738,200.
• Ben gets the gain first: his balance rises to $1,160,000, then falls to $946,000, then $764,100.

Both earned the same returns and the same average return, yet Ben ends roughly $25,900 ahead. With no withdrawals at all, both portfolios would finish at exactly $867,000 — the order only matters once money is being taken out. Anna sold a larger share of her portfolio at depressed prices in the first two years, and those shares were no longer invested for the recovery, leaving her on a lower path.

Over a full retirement the same mechanism can compound across many years, which is why a poor sequence early on is a serious planning risk. Possible responses include holding a cash or short-bond buffer, using a flexible withdrawal rule, or planning for some part-time income in the early years of retirement.

The 4% rule depends on a portfolio that generates real returns above inflation. Move too far from a balanced allocation and the safe rate changes:

• 100% stocks: An all-equity portfolio was one of the five allocations reported in the Trinity study. Its historical results should be interpreted alongside the other tested mixes rather than as evidence that more equity automatically produces a better withdrawal outcome.
• 75/25 stocks/bonds: One of the five mixes reported in the Trinity study, and close to the upper end of the 50–75% equity range Bengen favoured. The studies report results for specific portfolio mixes; they do not identify one universally optimal allocation.
• 50/50 stocks/bonds: Both Bengen and the Trinity research tested this allocation. In Bengen's historical test, using intermediate-term U.S. Treasuries, a 4% inflation-adjusted starting withdrawal lasted at least 30 years in every period he tested. The Trinity research used long-term corporate bonds, so results from the two studies are not directly interchangeable.
• 100% bonds: Historical results were substantially weaker than for the stock-and-bond mixes highlighted above. In the Trinity tests, a portfolio of long-term corporate bonds supported an inflation-adjusted 4% withdrawal in only a minority of 30-year periods, and even 3% did not succeed in every period.

The historical withdrawal research tested specific stock-and- bond mixes; it does not establish one correct allocation for every retiree. Your own mix depends on factors such as your horizon, other resources, tolerance for portfolio declines and the withdrawal method you plan to use.

• Retirement length beyond 30 years. A 45-year-old is planning for a horizon far longer than the one the classic rule was tested against, which generally argues for testing a lower starting rate rather than assuming 4%.
• Heavily bond-weighted portfolio. Long-run real returns are too low to support 4% indefinitely.
• High fee load. Advisory and fund fees reduce the returns available to support withdrawals, so higher costs can reduce what a portfolio can sustainably support. The withdrawal-rate figures discussed in this guide do not automatically account for your individual investment costs.
• Inflexible spending. If you can't reduce spending in a downturn, you carry more sequence risk.
• Non-US investors with home bias. Many international markets historically supported lower safe rates than the US.

• Significant Social Security or pension. Guaranteed income reduces the share your portfolio must cover.
• Willingness to flex spending. Reducing portfolio withdrawals after poor market returns can improve the sustainability of a withdrawal plan, but the trade-off is lower or more variable spending.
• Part-time work or side income. Income that covers part of your spending early in retirement reduces how much you withdraw from the portfolio during a sequence-sensitive period, which can reduce sequence-of-returns risk. It does not remove it: returns can still be poor, withdrawals usually continue, and the portfolio remains exposed to the order of future returns.
• Shorter horizon. A shorter retirement horizon generally supports testing a higher starting withdrawal rate, all else equal. The appropriate figure still depends on the horizon, portfolio, assumptions and methodology used.
• Inheritance or paid-off home. A paid-off home can reduce the spending your portfolio must cover, while home equity or a future inheritance may provide additional resources later. Neither automatically justifies a higher starting withdrawal rate, and an inheritance is uncertain in both timing and amount.

Guyton-Klinger guardrails

Adjust withdrawals up or down when the current withdrawal rate drifts outside preset bands: cut spending after the rate rises well above its starting level, and raise spending after it falls well below. In Guyton and Klinger's 2006 simulations, their full set of decision rules supported higher maximum initial withdrawal rates under specific portfolio and planning assumptions. The headline results depended on a 40-year horizon, portfolios with at least 65% equities, and rules that allowed spending cuts and skipped inflation increases along the way. These are model results, not a recommended starting rate, and real income can become more variable.

Source: Guyton & Klinger (2006), “Decision Rules and Maximum Initial Withdrawal Rates”.

Fixed-percentage withdrawal

Withdraw a fixed percentage of the current balance each year (e.g. 4% of whatever the portfolio is worth). The portfolio can never fully deplete, but income fluctuates significantly.

Bond tent / glidepath

Shift to a more conservative allocation around retirement, then gradually increase the equity share. Rising-equity glidepaths have been studied as a way to reduce exposure to poor returns around the start of retirement; in Pfau and Kitces' 2014 analysis they improved worst-case outcomes under the tested assumptions, not every outcome.

Source: Pfau & Kitces (2014), “Reducing Retirement Risk with a Rising Equity Glide Path”.

Cash bucket strategy

Hold a cash reserve for near-term expenses and refill it from investments when conditions allow. A cash reserve can reduce the need to sell volatile assets during a downturn, but it does not eliminate sequence risk: a prolonged downturn can exhaust the reserve, and cash held aside also participates less in market growth.

Dynamic SWR

Recalculate the safe withdrawal rate each year based on the remaining horizon and current portfolio. Mathematically robust, but income varies.

Example 1: A traditional retiree

Sara retires at 65 with $1,250,000 invested, 60/40 stocks/bonds. Using the 4% rule, she withdraws $50,000 in year one. After a 3% inflation year, she withdraws $51,500 in year two. Her 30-year horizon matches the period the original studies tested, though her exact 60/40 mix was not one of the allocations they reported.

Example 2: An early retiree

Marcus retires at 42 with $1,500,000 and expects a 50-year horizon — far longer than the 30 years the original research tested. A 4% starting rate would withdraw $60,000 in year one; a more conservative 3.5% scenario would withdraw $52,500, leaving $7,500 more invested. This is an illustrative comparison, not a recommended rate for his horizon, and it does not establish a particular probability of success.

Example 3: Flexible Barista FIRE

Priya semi-retires at 50 with $700,000 and a part-time income of $20,000. Her annual expenses are $48,000, so her portfolio must cover only $28,000 — a 4% withdrawal on $700,000. Her part-time income reduces the amount she needs to withdraw from the portfolio during the early years of retirement, which lowers — but does not remove — her exposure to a poor sequence of returns. See What is Barista FIRE? for the full pattern.

Example 4: Coast FIRE re-allocation

Jamal hits Coast FIRE at 35 with $400,000 invested and stops contributing. Assuming a constant 5% annual real return — an illustrative assumption, not a forecast — the portfolio would grow to about $1.73 million in today's dollars by 65, supporting a 4% withdrawal of roughly $69,000. See What is Coast FIRE?.

Model these scenarios against your own numbers in the Financial Independence Target Calculator — compare how different withdrawal-rate assumptions change the portfolio target for your annual spending.