How Much Do You Need to Retire? Finding Your Real Number

In 1994, a financial planner named William Bengen sat down with decades of historical stock and bond return data and asked a simple question: how much can a retiree pull from a portfolio each year without running out of money? His answer was 4% annually, and it has anchored retirement planning ever since.¹ The research was later confirmed by the Trinity Study in 1998, which ran the same analysis across a wider range of portfolios and time periods.² The 4% rule has real limits, which we'll get to, but as a starting framework it holds up well enough to build on.

The basic math is this: take whatever you expect to spend each year in retirement and divide by 0.04. That gives you the portfolio you need. If you plan to spend $60,000 per year, you need $1.5 million. If $100,000 is your number, you need $2.5 million. The logic behind the division is that a well-diversified 60/40 portfolio (60% stocks, 40% bonds) has historically grown fast enough to let you withdraw 4% annually while keeping pace with inflation, sustaining the portfolio for 30 years or more in roughly 95% of historical scenarios.²

Let's start with how to build your expense estimate, because getting that number right matters more than anything else in the calculation.

What You're Actually Going to Spend

Most people underestimate retirement spending, especially in the first decade. Housing is usually the biggest line: mortgage or rent, property taxes, insurance, maintenance, and utilities together run $2,150 to $4,450 per month depending on where you live and whether the house is paid off. Healthcare comes next, and it surprises people. Medicare Part B premiums, supplemental (Medigap) coverage, and out-of-pocket costs combine to $900 to $1,700 per month for a typical retiree.³ Add groceries, transportation, phone and internet, dining out, travel, and hobbies, and most retirees land between $60,000 and $80,000 per year in total spending, though your specific lifestyle and location can push that number significantly higher or lower.

The IRS has a useful framing here: its free withholding estimator and tax tables show exactly how ordinary income from retirement accounts gets taxed, which affects how much you actually need to withdraw to land a given spending level.⁴ A $60,000 spending goal pulling from a traditional 401(k) might require withdrawing $75,000 or more once federal taxes are factored in, which means your real portfolio target is higher than the raw 4% math suggests. Roth IRA withdrawals avoid this problem entirely, since qualified distributions come out tax-free, which is one reason building Roth balances alongside traditional accounts is worth the effort early on.

The Inflation Problem Nobody Visualizes Well

The number above is the one that catches people off guard. You plan for $60,000 per year, but you retire in 20 years. At 3% annual inflation, a historically reasonable assumption based on long-run Consumer Price Index data,⁵ that same standard of living costs over $108,000 per year by then. In 30 years it's over $145,000. The 4% rule accounts for this because the portfolio itself is expected to grow at roughly 7% to 8% annually in a diversified portfolio over the long run, which stays well ahead of 3% inflation. But the accounting only holds if you're withdrawing from a portfolio that's actually invested for growth, not sitting in cash.

If you're 35 and plan to retire at 65, your real expense target is what that spending looks like in 2055 dollars, not today's. That's worth calculating once, concretely. Try the retirement calculator at /tools/retirement to run the numbers with your actual timeline.

How Social Security Changes the Calculation

Now shift to the part that can reduce your target by hundreds of thousands of dollars. Social Security is a guaranteed, inflation-adjusted income stream, and most people underweight it when calculating how much they need to save.

The Social Security Administration reports that the average retired worker benefit in 2024 runs roughly $1,907 per month, or about $22,900 per year.⁶ That varies enormously based on your earnings history and when you claim. Claiming at 62 locks in a permanently reduced benefit; waiting until 70 can increase it by 76% compared to claiming at 62. For someone with a solid earnings history claiming at 67 (full retirement age for those born after 1960), $2,400 per month, or $28,800 per year, is a reasonable ballpark.

Here is what that does to your portfolio target. Suppose you need $70,000 per year in retirement. Social Security covers $28,800 of that, so your portfolio only needs to generate $41,200 per year. Divide by 0.04 and your required portfolio drops to $1.03 million rather than $1.75 million. That $720,000 gap is enormous, and it means the exact timing of when you claim Social Security is one of the highest-leverage decisions in your retirement plan. The SSA's own benefit estimator at ssa.gov/estimator lets you model different claiming ages against your actual earnings record.⁶

When Other Income Streams Enter the Picture

Passive income works the same way. Every $10,000 per year you bring in from dividends, rent, a pension, or another reliable source reduces the portfolio you need by $250,000. The math is just the inverse of the 4% rule: $10,000 divided by 0.04 equals $250,000, meaning that $10,000 per year is worth $250,000 in portfolio terms when you're building your retirement target.

Run that through a realistic scenario. Suppose you own a rental property generating $20,000 per year in net cash flow after expenses. Combined with $28,800 in Social Security, that leaves only $21,200 per year for your portfolio to cover against a $70,000 spending target. Your required portfolio becomes $530,000 instead of $1.75 million. The rental does the heavy lifting of a million-dollar account. This is why people who spend their working years building passive income sources often find they need to accumulate far less in investable assets than a pure 4% calculation implies.

What Early Retirement Really Costs

Let's be honest about the early-retirement math, because this is where a lot of optimistic plans run into trouble. Retiring at 55 instead of 65 adds ten more years of withdrawals, removes ten years of contributions, and delays Social Security. Those three forces stack in the wrong direction simultaneously.

In the same $70,000-per-year scenario, retiring at 55 means Social Security is not available yet (the earliest claiming age is 62, and claiming that early comes with a permanent reduction). You need the full $70,000 from your portfolio, which means $1.75 million. Waiting until 65 drops that to $1.03 million because Social Security is immediately available. The difference is $720,000, and that is the rough cost of ten years. Each year earlier you retire adds somewhere between $70,000 and $100,000 to the target you need to reach, and that cost compounds because you also have ten fewer years of salary coming in to fund the accumulation.

A Worked Plan at 35

Here is how all the pieces connect for a specific person. You are 35, planning to retire at 65, and expect to spend $70,000 per year. Your expected Social Security at 67 is $2,400 per month.

Step one: the base formula gives you $70,000 divided by 0.04, which equals $1,750,000.

Step two: Social Security covers $28,800 per year, reducing your portfolio's required annual output to $41,200. Divide by 0.04 and your actual target becomes $1,030,000.

Step three: with 30 years until retirement and an 8% average annual return on a diversified portfolio, reaching $1,030,000 from zero requires roughly $760 per month in contributions. The math comes from a compound growth factor of 113.3 for 8% over 30 years: $1,030,000 divided by 113.3 equals $9,090 per year, or about $760 per month.¹

If you also build a modest passive income stream, say a rental property generating $12,000 per year by retirement, your required portfolio shrinks by $300,000 and the monthly contribution needed drops closer to $550. These numbers shift with your actual return assumptions, contribution timing, and inflation rate, which is why the retirement calculator is worth spending time with once you have your baseline.

The Conservative Case for Adjusting the 4% Rule

The Trinity Study ran on 30-year horizons. If you retire at 55 and live to 95, you are looking at a 40-year horizon, and the failure rate at 4% starts to climb at those extended lengths. Some researchers now argue 3.3% to 3.5% is a more defensible withdrawal rate for long retirements, while others point out that most retirees reduce spending naturally in their late 70s and 80s, which gives the portfolio room to recover in down markets.²

The practical middle ground is this: use 4% to set your target, build in a margin by targeting a number slightly above the formula, and plan to stay flexible in the first five years of retirement. Pulling back withdrawals by 5% to 10% in a bad market year dramatically improves long-term outcomes. The 4% rule is a floor, not a ceiling, and treating it as the precise answer to a 40-year question gives it more authority than Bengen himself intended.

Overall, retirement planning comes down to one honest calculation and a few variables that can move it substantially: how much you spend, when you claim Social Security, what you earn from passive income, and how long your money needs to last. Run those numbers with real figures from your own life, not round estimates. The readers who struggle in retirement are almost always the ones who never did the math at all, not the ones who found out the answer was inconvenient. Find out now.