Ask people how much they need to retire, and there is a good chance they can throw out a number almost instantly. Maybe it is $1 million because that is what they have always heard, or $2 million because some calculator somewhere told them that is a good number.
You could also say $3 million, because it sounds safer than $2 million. But in a real sense, none of it matters, because all of these figures sound concrete, and that is precisely what makes them dangerous. Most retirement numbers rest on an assumption so flawed it can quietly invalidate the entire calculation.
Those two words are “spending rate.” Not investment returns, not portfolio size. The number you actually need in retirement is almost entirely determined by what you plan to spend. Most people either significantly underestimate that figure or borrow it from a generic formula that has nothing to do with their real lives.
Where the Standard Formula Breaks Down
The 4% rule is the most widely cited framework in retirement planning. Financial planner Bill Bengen developed it in 1994 after analyzing U.S. market data going back to 1926. The rule holds that withdrawing 4% of your portfolio annually gives the money a reasonable chance of lasting 30 years. So $1 million supports roughly $40,000 a year in withdrawals, while $2 million supports $80,000, and so on.
The rule has been updated and debated many times since. Morningstar’s December 2025 research set 3.9% as the safe starting withdrawal rate for retirees in 2026, up from 3.7% the prior year, based on forward-looking return and inflation projections targeting a 90% success rate over 30 years with a balanced portfolio. Bengen himself has revised his figure upward, most recently suggesting 4.7% as the historical worst-case safe rate.
The deeper problem, though, is that the rule says nothing about whether the resulting dollar amount is actually enough. It tells you only how long the money will last at a given withdrawal rate. If your real spending is $120,000 a year, a $1 million portfolio does not fund your retirement under the 4% rule. A $3 million portfolio does. The formula is only useful once you have honestly solved for spending first, and most people skip that step entirely.
Standard formulas also struggle to absorb current structural cost shifts. While broad inflation has cooled from its 2022 peak of 9.1%, the consumer price index still ran at 3.8% as of April 2026. More importantly, baseline costs for essential services, property insurance, auto premiums, and medical care have settled at a permanently higher floor. A retirement spending plan built on pre-2022 historical baselines can be underfunded from day one.
The Spending Number Most People Get Wrong
Two common mistakes come up when people estimate retirement spending. The first is assuming they will spend less than they do now. Sometimes that is true: the mortgage may be paid off, the kids are gone, commuting costs disappear. But healthcare spending rises sharply with age, travel often increases in the early retirement years, and lifestyle costs do not evaporate just because a paycheck does.
The healthcare line deserves its own spotlight. According to Fidelity Investments’ 2025 Retiree Health Care Cost Estimate, a 65-year-old retiring in 2025 can expect to spend an average of $172,500 on healthcare and medical expenses over the course of retirement, not counting long-term care. That figure is up more than 4% from the 2024 estimate of $165,000, and it has nearly doubled from Fidelity’s inaugural $80,000 estimate back in 2002. For couples, the total reaches roughly $345,000. Medicare helps, but it does not eliminate out-of-pocket costs: the standard monthly Part B premium alone jumped to $202.90 in 2026, a nearly 10% increase from 2025.
Lifestyle inertia compounds the underestimation problem. Digital subscriptions, recurring service fees, and daily routines that fill the hours once occupied by a commute can match or exceed what working life cost in operational expenses. These costs are real but easy to overlook when building a spending projection.
The second common mistake is forgetting to account for inflation across a long retirement. The average U.S. retirement age is around 62, according to multiple recent surveys, which means many retirees face a horizon of 25 years or more. A spending level that feels comfortable at the start of retirement can become genuinely strained a decade in, especially if the portfolio is not built to keep pace with rising costs.
Why the Number Feels Right Until It Isn’t
The retirement number problem is insidious because it stays invisible for years. You save toward a goal, hit it, and feel a genuine sense of arrival. Then you retire, and sometime in year two or three, the math does not work the way you assumed. By that point, the options for correcting course are narrower and less comfortable than they would have been with more careful planning upfront.
This is especially common among people who anchor to a round number like $1 million or $2 million without ever working backwards from actual spending. The number feels ambitious enough to be credible, so the hard question never gets asked: what does my life actually cost, and what does it cost to fund that life for 25 or 30 years?
Beyond Fixed Math: The Retirement Smile Curve
Actual retirement spending rarely follows a straight line. Financial researcher David Blanchett coined the term “retirement spending smile” in a 2014 Journal of Financial Planning paper to describe the pattern his research revealed in thousands of retiree households. In the active “go-go” years of early retirement, spending tends to spike as travel, hobbies, and delayed lifestyle goals take center stage. That phase transitions into more moderate “slow-go” middle years as daily activity naturally slows. Then the “no-go” later years introduce a fresh surge in costs, driven primarily by healthcare, specialized support, and assisted living needs.
Linear drawdown rules often overfund the quiet middle years while leaving the late-stage bookend exposed to compounding medical costs. Recognizing the curve, rather than assuming a flat spending trajectory, gives a more honest picture of where the money actually needs to go.
How to Build the Right Number Instead
The correct sequence is the reverse of how most people approach it. Start with spending, not savings. Build a detailed picture of what your retirement actually looks like: where you live, how often you travel, what healthcare will cost, what you want to leave behind. Then price it out honestly. From there, work backwards to determine the portfolio size needed to fund that life at a withdrawal rate you are comfortable sustaining.
If you need $100,000 a year and use a conservative 4% withdrawal rate, your number is $2.5 million. If you prefer the extra cushion of a 3.5% rate, it is closer to $2.86 million. Neither of those is a generic answer. They are your answer, built from your actual life. To navigate shifting spending phases, many modern plans now use dynamic guardrails: annual distributions adjust up or down based on real portfolio performance rather than a fixed index, which can improve both sustainability and spending confidence over time.
The retirement number is not a savings milestone. It is a spending problem. Solve for spending first, and the number will follow.
Editor’s note: This version adds Morningstar’s December 2025 updated safe withdrawal rate of 3.9% for 2026 retirees, Fidelity’s 2025 lifetime healthcare cost estimate of $172,500 per individual (up from $165,000 in 2024), the 2026 Medicare Part B premium of $202.90 per month, and attribution for the retirement spending smile to David Blanchett’s 2014 Journal of Financial Planning research.
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