How the 4 Percent Rule Works for Retirement Planning

What Is the 4% Rule?

The 4% rule is a retirement withdrawal guideline that says you can withdraw 4% of your investment portfolio's value in your first year of retirement, then increase that same dollar amount every year after to keep up with inflation, with a strong historical likelihood your money lasts at least 30 years.

It's sometimes described the opposite way: if you've saved 25 times your annual expenses, you've hit your "number." Both descriptions point to the same math, since 1 divided by 4% equals 25.

The 4% figure isn't a tax rate, an interest rate, or a guaranteed return. It's a withdrawal rate — a starting point for how much of your own savings you draw down each year, calculated once at retirement and then simply adjusted for inflation from there.

What Counts as Your "Portfolio"

For this calculation, your portfolio means investable retirement savings: 401(k) and 403(b) balances, traditional and Roth IRAs, and taxable brokerage accounts. It doesn't include your home equity, a pension, or Social Security — those are separate income sources that sit outside the 4% calculation entirely, a point we'll come back to later in this guide.

Where the 4% Rule Comes From

The 4% rule didn't come from a bank or a government agency. It came from two pieces of research, done about a decade apart, that asked the same basic question: looking at real historical market returns, how much could a retiree have safely spent each year without running out of money?

William Bengen's Original Research (1994)

Financial planner William Bengen published the idea in the Journal of Financial Planning in October 1994. He tested rolling 30-year retirement periods back to 1926, using a stock-and-bond portfolio, and asked what withdrawal rate would have survived every period in his data — including the worst one, a retiree who began withdrawals on October 1, 1968, right before a prolonged bear market and the high inflation of the 1970s. (Advisor Perspectives) Even that scenario survived a 4.15% withdrawal rate, which Bengen rounded down to 4% and called the SAFEMAX — the maximum "safe" rate his data could support.

The Trinity Study (1998)

A few years later, three professors at Trinity University in Texas — Philip Cooley, Carl Hubbard, and Daniel Walz — ran a similar analysis with a different lens: instead of one worst-case number, they calculated a success rate across every rolling 30-year period in the historical data.

For a portfolio split evenly between stocks and bonds, a 4% initial withdrawal rate, adjusted for inflation every year after, succeeded in about 95% of the 30-year periods they tested. (Financial Planning Association) That's the study most people are actually referencing when they mention "the 4% rule," even though Bengen's work came first.

How the 4% Rule Works, Step by Step

The mechanics of the 4% rule are simpler than the research behind it. Here's the actual process:

1. Add up your total portfolio value on the day you retire — 401(k)s, IRAs, and taxable brokerage accounts, not your home or Social Security.
2. Withdraw 4% of that total in your first year of retirement.
3. In every year after that, increase the dollar amount, not the percentage, by that year's inflation rate.
4. Keep withdrawing that inflation-adjusted figure every year, regardless of what the market does in the meantime.

A Simple Multi-Year Walkthrough

Say you retire with a $1,000,000 portfolio:

• Year 1: $1,000,000 × 4% = $40,000
• Year 2 (assume 3% inflation): $40,000 × 1.03 = $41,200
• Year 3 (assume 3.2% inflation): $41,200 × 1.032 ≈ $42,518

Your spending grows steadily with prices, regardless of whether your portfolio went up or down that year. That consistency is the main selling point of the rule — and also its biggest limitation, which comes up in the next couple of sections.

A 4% Rule Example: Turning Savings Into Income

The 4% rule becomes a lot more concrete once you plug in real numbers. Here's what a 4% initial withdrawal looks like across a range of portfolio sizes.

Notice how directly the withdrawal amount scales with portfolio size — doubling your savings simply doubles your year-one income under this rule. On a $1,000,000 portfolio, that $40,000 first-year withdrawal grows to roughly $41,200 in year two at 3% inflation, and keeps climbing from there, regardless of how the market performs in any given year.

Fewer people hit that $1 million mark than you'd guess from how often it comes up in retirement conversations. According to an Employee Benefits Research Institute analysis of Federal Reserve data, fewer than 5% of Americans have $1 million or more saved for retirement, and the figure is closer to 3% among people who are already retired. (SmartAsset) That doesn't mean $1 million is required to retire — run the math above on your own numbers instead of a round figure that gets repeated a lot.

How Long Will Your Money Last Using the 4% Rule?

The 4% rule is built around a 30-year time horizon, which maps reasonably well to someone retiring in their mid-60s and living into their 90s. In the original research, a 4% initial withdrawal rate with a stock-and-bond portfolio succeeded — meaning the portfolio still had money left — in about 95% of the historical 30-year periods tested.

That 95% figure gets misread a lot. It doesn't mean you personally have a 95% chance of success — it means this withdrawal rate worked in about 95% of the rolling 30-year periods in roughly a century of market history. Your actual outcome still depends on the specific sequence of returns you experience.

Sequence of Returns Risk

The order your returns arrive in matters just as much as their average. Two retirees with identical average 30-year returns can end up in very different places if one hits a downturn in year one or two of retirement and the other doesn't — a pattern called sequence of returns risk, and the single biggest reason the 4% rule isn't a guarantee. Withdrawing a fixed, inflation-adjusted dollar amount from a portfolio that's already shrunk early on can permanently shorten how long the money lasts, even if the market recovers later.

What Happens Beyond 30 Years

If you're planning for a longer retirement — because you're retiring early, or simply expect to live a long time — a 4% withdrawal rate becomes noticeably less safe. Research modeling a 40-year retirement horizon generally puts the safe starting withdrawal rate closer to 3.2%, and a 50-year horizon pushes it lower still. If your retirement could realistically stretch past 30 years, treat 4% as a number to test against your own plan, not one to lock in automatically.

What the 4% Rule Doesn't Account For

The 4% rule is a useful starting point, but it was built to answer one narrow question: how much can you withdraw from an investment portfolio and have it last 30 years? It was never designed to capture everything else going on in a real retirement.

Does the 4% Rule Include Social Security?

No. The 4% rule applies only to your investment portfolio — 401(k)s, IRAs, and taxable accounts. Social Security, pensions, rental income, and part-time work are all separate income sources that sit outside the calculation entirely.

Most people don't need their portfolio to cover 100% of spending. A more realistic approach: estimate your total annual spending, subtract whatever you'll receive from Social Security or a pension, and apply the 4% rule only to the remaining gap. Someone who needs $70,000 a year and expects $28,000 from Social Security only needs their portfolio to supply $42,000 — a target of $1,050,000, not the $1,750,000 they'd need if the rule had to cover their full spending alone.

Does the 4% Rule Preserve Principal?

Not by design, but often in practice. The rule is built to draw your portfolio down over 30 years, not protect your original balance. But because the withdrawal amount is based on your starting balance and then just adjusted for inflation — not recalculated as a percentage of your current balance — reasonable market returns can grow it faster than you're withdrawing. In many historical scenarios researchers have studied, retirees who stuck with a 4% (or more conservative) rate ended up with a similar or larger balance after 30 years than they started with — not guaranteed, but not prevented by the rule either.

Taxes

The 4% figure is typically pre-tax. Withdrawals from a traditional 401(k) or IRA owe income tax the year you take them out, while Roth withdrawals are generally tax-free in retirement, assuming you meet the account's holding requirements. Two people withdrawing the same dollar amount can end up with very different amounts to actually spend, depending on which accounts that money comes from.

Healthcare and Long-Term Care

Medical costs, especially later in life, tend to rise faster than general inflation, and long-term care in particular can be a major, unpredictable expense that a flat, inflation-adjusted withdrawal doesn't anticipate. It's worth budgeting for this separately rather than assuming a standard withdrawal will stretch to cover it.

Your Spending Won't Stay Flat

Retirement spending in real life rarely moves in a straight line. Many retirees spend more in the earlier, more active years of retirement, less through a comfortable middle stretch, and more again later on as healthcare needs increase — a pattern sometimes called the retirement spending "smile." The 4% rule assumes flat, steadily inflating spending, which is a reasonable simplification but not necessarily how your own budget will actually look.

Does the 4% Rule Still Hold Up Today?

This is one of the more actively debated questions in retirement planning, and reasonable experts land in different places.

The Case for a Lower Number

Morningstar publishes an annual "State of Retirement Income" report that estimates a safe starting rate using forward-looking market assumptions rather than pure history. For retirees starting in 2026, that research points to a more conservative 3.9% for a fixed, inflation-adjusted withdrawal over 30 years, with a 90% probability of the money lasting. (Morningstar) The figure has moved around in recent years, from roughly 3.3% to 4.0%, since today's asset prices, interest rates, and inflation expectations don't always mirror the historical averages Bengen and the Trinity researchers relied on.

The Case for a Higher Number

On the other side, Bengen himself has revisited his original research with updated data and a more diversified portfolio mix, and now puts his own SAFEMAX closer to 4.7%, calling the original 4% conservative for many retirees. (CNBC) His argument: broader diversification and a fuller historical dataset support a somewhat higher starting rate than his 1994 estimate.

What This Actually Means for You

Both of these are legitimate, well-researched positions, and the gap between them — roughly 3.9% to 4.7% — says less about which side is "right" and more about how sensitive this kind of forecasting is to the assumptions behind it. A few takeaways apply regardless of which side you lean toward:

• Treat 4% as a reasonable starting point to test against your own numbers, not a fixed rule.
• A flexible strategy — spending a little less in years the market performs poorly, a little more when it performs well — tends to outperform a rigid fixed withdrawal either way this debate settles.
• Your own time horizon, health, other income, and comfort with risk matter more than any single published percentage.

If you want a deeper look at this specific debate, our companion guide on whether the 4 percent rule is still safe for retirees today walks through more of the current research.

Retiring Early or Late: Does the 4% Rule Change?

The 4% rule was built around a 30-year retirement, which is a reasonable estimate for someone retiring around 65. Retire much earlier or later than that, and the math underneath the rule starts to shift.

Does the 4% Rule Work If You Retire at 55?

Retiring at 55 instead of 65 can easily mean a 40-year retirement instead of a 30-year one, and that extra decade matters — longer horizons give downturns more chances to strike early and give inflation more years to compound against a fixed withdrawal. Research on longer horizons generally suggests a starting rate somewhat below 4%, often 3.2% to 3.5% depending on portfolio mix.

That doesn't make early retirement unrealistic. It means early retirees typically need a larger portfolio relative to spending, a lower starting rate, or more flexibility to cut spending in a bad market year — the kind of planning the FIRE movement (Financial Independence, Retire Early) is built around. Our guides on how the FIRE movement works and how to calculate your FIRE number both dig into this in more detail.

Can I Retire at 60 With $1 Million?

Using the standard 4% rule, $1 million supports $40,000 in year-one withdrawals, or about $3,333 a month, before taxes and before adding Social Security or other income. Whether that's enough depends on your expected expenses, where you live, whether your mortgage is paid off, and how much other income you'll add on top. A retiree with modest expenses and a paid-off home may find this comfortable; someone with higher fixed costs may need a larger portfolio or a longer runway. It's a personal budgeting question as much as a withdrawal-rate one, so run your own numbers rather than leaning on the round $1 million figure alone.

Retiring at 70 or Later

A shorter time horizon works in your favor. If you're retiring at 70 with a life expectancy of 20 to 25 years instead of 30, the historical success rates for a 4% (or even a somewhat higher) withdrawal rate improve, since there's less time for a bad sequence of returns to do lasting damage.

Common Mistakes With the 4% Withdrawal Rule

A handful of habits consistently trip people up when they try to apply the 4% rule to their own retirement:

• Recalculating 4% of the current balance every year, instead of increasing the original dollar withdrawal for inflation. This turns a steady income plan into one that swings with the market.
• Forgetting the 4% figure is pre-tax. Withdrawals from traditional 401(k)s and IRAs are taxed as income, which reduces what actually lands in your pocket.
• Applying the rule to total spending instead of the gap left after Social Security and other income, which overstates how large a portfolio you actually need.
• Ignoring your own time horizon. A rule tested for 30 years doesn't automatically hold for a 40-year early retirement, or adjust itself for a shorter one.
• Panic-selling during a downturn instead of sticking with the plan, which locks in losses at exactly the wrong time.
• Treating 4% as fixed forever instead of revisiting the plan every few years as your portfolio, health, and spending change.
• Ignoring one-time costs, like a new roof or a major dental procedure, that don't fit neatly into a steady annual withdrawal.

What to Do If You're Running Out of Money in Retirement

If a market downturn or a string of bad years has your portfolio dropping faster than planned, a few practical options exist before things become an emergency:

• Reduce discretionary spending temporarily. Travel, dining out, and other flexible categories are usually easier to cut back than fixed costs.
• Delay Social Security if you haven't claimed it yet. Waiting past your full retirement age, up to age 70, increases your monthly benefit for life.
• Consider part-time or consulting work, even temporarily, to reduce how much you need to withdraw during a rough market stretch.
• Revisit your withdrawal strategy. Dynamic approaches, like the Guyton-Klinger "guardrails" method, adjust spending up or down based on how the portfolio is actually performing, rather than sticking to one fixed number regardless of conditions.
• Talk to a fee-only financial planner. A professional can model your specific situation, something a general rule of thumb was never built to do.

Building a Retirement Withdrawal Plan That Fits Your Life

The 4% rule is a starting point, not a finished plan. Here's a practical sequence for turning it into something that actually fits your situation:

1. Estimate your real annual spending, based on your actual budget, not a rough guess.
2. Add up guaranteed income you'll receive from Social Security, a pension, or an annuity.
3. Subtract that guaranteed income from your spending target to find the gap your portfolio needs to cover.
4. Apply a starting withdrawal rate to that gap, based on your time horizon — somewhere in the 3.5% to 4.7% range most current research supports.
5. Build in flexibility. Decide in advance how you'll adjust spending in a strong market year versus a weak one.
6. Revisit the plan every year or two, especially after major life changes or significant market moves.

100 Calculator's 4 Percent Rule Calculator can handle the year-by-year math for step four automatically once you know your target withdrawal amount, and our FIRE Financial Independence Calculator can help with the reverse question — how large a portfolio you'd need to support a given retirement budget.

Tools to Help You Plan Your Retirement Withdrawals

A handful of free calculators can take the manual math out of everything covered above:

• 4 Percent Rule Calculator — enter your portfolio value to see your year-one withdrawal and how it grows with inflation over time.
• FIRE Financial Independence Calculator — work backward from your target retirement spending to figure out how large a portfolio you actually need.
• Premium Compound Interest Calculator — model how your portfolio might grow before retirement, which directly shapes how much a 4% withdrawal will eventually be worth.
• Daily Compound Interest Calculator — see how contribution frequency and compounding periods affect long-term growth while you're still saving.
• Premium Simple Interest Calculator — useful for comparing straightforward, non-compounding growth on cash you might hold as a short-term income buffer.

More From Our Finance Guide

Still building out your retirement or savings strategy? These related guides dig deeper into the topics covered above.

Frequently Asked Questions