Only 3 Numbers Really Matter for Retirement — Do You Know Yours?

Deciding whether you are ready to retire can feel overwhelming, but the question ultimately comes down to three concrete numbers. Get a clear handle on all three and the answer becomes much easier to see.

Here is what those numbers are and why each one carries so much weight.

1. Investment account balance

The first number you need is your total investment account balance: the combined value of your 401(k), IRA, and any taxable brokerage accounts. These savings will supplement your Social Security income once you stop working, which makes knowing the precise figure essential. Tax treatment matters just as much as the raw balance. A dollar in a traditional 401(k) will eventually shrink when income taxes come due at withdrawal, while money in a Roth IRA comes out entirely tax-free. The two accounts may show the same number on paper, but they carry meaningfully different real-world values.

Once you know your total balance, a safe withdrawal rate tells you how much annual income those savings can reliably produce. Morningstar’s 2025 “State of Retirement Income” research sets the base-case safe starting withdrawal rate at 3.9% for a portfolio holding 30% to 50% in equities, assuming a 30-year retirement horizon with a 90% probability of success. That rate climbed from 3.7% in the prior year’s research, driven by improved capital markets assumptions across nearly every asset class. For a retiree with $850,000 saved, the 3.9% figure translates to roughly $33,150 in first-year income from savings alone.

Morningstar also found that flexible strategies, including a guardrails spending approach, delaying Social Security, or incorporating Treasury Inflation-Protected Securities, can push the starting withdrawal rate as high as 5.7% for retirees willing to adjust their spending as market conditions shift. The classic 4% rule remains a widely cited benchmark, but those who want the greatest margin of safety may prefer the slightly more conservative Morningstar figure. Retirees comfortable making dynamic adjustments in down markets can often stretch their withdrawal rate meaningfully higher.

2. Social Security benefit

The second number is your projected Social Security benefit. This monthly payment stands apart from a portfolio balance because it is guaranteed to last for life and automatically adjusts for inflation each year. For 2026, the Social Security Administration announced a 2.8% cost-of-living adjustment, raising the average retired worker’s monthly benefit from approximately $2,015 to about $2,071 starting in January. By mid-2026, the average monthly benefit for retired workers had climbed further to roughly $2,083, reflecting the mix of new retirees and those whose earnings history produces above-average checks. The 2.8% COLA reflects changes in the Consumer Price Index for Urban Wage Earners and Clerical Workers, and it marks the fifth consecutive year with an adjustment of at least 2.5%, the longest such streak since the 1990s.

Social Security is designed to replace roughly 40% of pre-retirement income, though the actual share varies by earner. The benefit formula is progressive, so higher earners see a smaller percentage replaced. Timing matters just as much as the formula itself. Claiming benefits before your full retirement age permanently reduces each monthly check, while waiting past full retirement age earns delayed retirement credits worth roughly 8% for every year you hold off, up to age 70. For those expecting a long life, or for married couples trying to maximize the survivor benefit, delaying almost always pays off.

Calculating your personal breakeven point for waiting until 70 can clarify whether the larger monthly checks eventually outweigh the years of missed payments. You can find your personalized estimate through your online Social Security account, which projects your monthly payment at different claiming ages. The size of this benefit directly shapes how much your savings need to carry.

3. Annual expenditures

The third number is your projected annual spending. Your combined income from Social Security and savings must cover everything you plan to spend in retirement, including costs that many people consistently underestimate. Healthcare belongs at the top of that list. Fidelity’s 25th annual Retiree Health Care Cost Estimate, released in July 2026, puts lifetime medical expenses for a single 65-year-old retiring in 2026 at $185,500, a jump of 7.5% from the prior year’s estimate of $172,500. Three forces are driving that increase: rising prices for medical care, growing utilization of healthcare services, and higher costs tied to chronic conditions. The estimate excludes long-term care. For a couple, Fidelity’s comparable 2026 figure reaches $371,000.

Medicare costs add another layer of annual pressure. The 2026 Medicare Part B standard premium is $202.90 per month, an increase of $17.90 from the 2025 rate of $185.00. The annual Part B deductible rose to $283 in 2026, up $26 from $257 in 2025. Both figures have moved higher in every recent year, which is why healthcare costs require their own dedicated line in any retirement plan, separate from general living expenses.

A practical starting point for your retirement spending target is aiming for enough income to replace about 80% of pre-retirement earnings. Keep in mind that many retirees follow what researchers call a “spending smile” pattern: outlays are highest in the active early years, ease off during the quieter middle stretch, and then climb again as medical costs rise later in life. A budget that reflects this arc gives a more accurate picture than one that assumes flat annual spending throughout retirement.

Once you have all three numbers in hand, the final step is to stress-test them against sequence-of-returns risk. A severe market decline in the first few years of retirement can permanently deplete a portfolio before it has a chance to recover, even if the long-run average return looks reasonable on paper. Retirees who account for that risk alongside their balance, their benefit, and their budget are far better positioned to leave work on their own terms.

Editor’s note: This pass corrects the Morningstar equity allocation range back to 30% to 50% (the figure cited in Morningstar’s own published research for the 3.9% base-case) and removes unverifiable 2027 Medicare Trustees Report projections that appeared in a prior version; it also adds mid-2026 SSA data showing the average retired-worker benefit had reached approximately $2,083 per month by that point.

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