Most people check their retirement account balance occasionally, feel vaguely uneasy or vaguely satisfied, and move on. What they rarely do is calculate whether that balance is actually sufficient to fund retirement at their expected spending level for as long as they're likely to live.
These are answerable questions. They're not simple, because they depend on variables you have to estimate, but the framework for answering them is well-established. Understanding the four key outputs of a retirement readiness analysis, projected nest egg, sustainable withdrawal rate, income gap, and the contribution needed to close that gap, gives you a picture that's far more actionable than a raw balance figure.
What a Nest Egg Projection Actually Means
A nest egg projection takes your current savings balance, your expected annual contributions, an assumed investment return rate, and the number of years until your target retirement age, and calculates what your portfolio will likely be worth at retirement.
The math is straightforward compound growth: future value = present value * (1 + r)^n, plus the future value of your ongoing contributions. What makes the projection useful or misleading is the return rate assumption. Historically, U.S. stock market index funds have returned roughly 10% annually before inflation, or 6% to 7% after inflation. Using nominal returns to project future wealth but then spending in today's dollars creates a systematic error. The better approach is to use real (inflation-adjusted) returns throughout.
A 35-year-old with $80,000 saved, contributing $10,000 per year, at a 6% real return, has a projected nest egg of approximately $1.1 million at age 65. At a 7% real return, the figure is about $1.35 million. The choice of return assumption matters, which is why running projections at multiple rates is more useful than relying on a single number.
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The free retirement readiness calculator by EvvyTools runs this projection, adjusts for inflation, and produces the result alongside the other key outputs. It also calculates your Coast FIRE number, which is the amount at which your current savings would grow to your retirement target without any additional contributions. If your current balance exceeds your Coast FIRE number, you've already done enough saving, even if you stopped contributing today.
The Sustainable Withdrawal Rate
Having $1 million saved doesn't tell you how much you can spend each year. That's determined by your withdrawal rate and how long your portfolio needs to last.
The widely cited safe withdrawal rate comes from research, particularly the Trinity Study, that examined historical 30-year periods in the U.S. stock market and concluded that a 4% initial withdrawal rate, adjusted for inflation each year, produced a portfolio that survived all historical 30-year periods with at least some assets remaining. The 4% rule is a useful starting point but not a universal prescription.
A retirement that starts at 55 might last 40 years, not 30. A 4% withdrawal rate carries more risk over 40 years than over 30. Research suggests that retiring early with a longer horizon warrants a lower initial withdrawal rate, perhaps 3.5% or 3.25%, to maintain reasonable survival probability. Conversely, someone retiring at 70 with a shorter expected horizon can reasonably use a higher withdrawal rate.
At 4%, a $1 million portfolio supports $40,000 per year in initial withdrawals, adjusted upward each year for inflation. At 3.5%, the same portfolio supports $35,000. The choice of withdrawal rate is one of the most consequential inputs in retirement planning.
The Income Gap and How to Close It
The income gap is the difference between your expected annual retirement expenses and your expected non-portfolio income. Non-portfolio income typically includes Social Security, any pension, rental income, or part-time work.
The Social Security Administration lets you estimate your expected benefit based on your earnings history. The timing of when you claim matters significantly. Claiming at 62, the earliest eligibility age, produces a benefit roughly 25% to 30% lower than waiting until full retirement age (66 to 67 depending on birth year). Waiting until 70 produces a benefit about 32% higher than full retirement age. For most people who expect to live into their 80s, delaying Social Security is financially advantageous.
Once you estimate Social Security income, subtract it from expected annual expenses. The remainder is your income gap, the portion your portfolio needs to fund. Dividing the income gap by your withdrawal rate gives you the target portfolio size.
For example: if you expect $60,000 in annual expenses and $22,000 in Social Security income, your income gap is $38,000. At a 4% withdrawal rate, the target portfolio is $38,000 / 0.04 = $950,000. If you project to have $1.1 million, you have a surplus. If you project $700,000, you have a shortfall of $250,000 and need to either increase contributions, reduce expected spending, delay retirement, or accept some income gap in early retirement.
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Sensitivity Analysis: Why One Projection Isn't Enough
Retirement projections depend on assumptions that are inherently uncertain. Return rates fluctuate. Inflation varies. Life expectancy is unpredictable. A single projection at 6% real return and a 4% withdrawal rate gives you one number, but it doesn't tell you how sensitive you are to those assumptions being wrong.
A sensitivity matrix shows you how your retirement outcome changes across combinations of return rates and withdrawal rates. Running your numbers at 5%, 6%, and 7% real return against 3.5%, 4%, and 4.5% withdrawal rates produces a 3x3 table that shows you your best, baseline, and stress-case scenarios. This is more informative than any single estimate.
The EvvyTools retirement readiness calculator includes a sensitivity matrix that covers this range automatically. It also provides an income waterfall breakdown showing how different income sources, portfolio withdrawals, Social Security, and any other income, stack up against expected expenses across retirement years.
The Role of the Coast FIRE Number
The Coast FIRE number is a particularly useful intermediate milestone. It answers the question: how much do I need saved today such that, even with no further contributions, my savings will compound to my retirement target by my target retirement age?
At a 6% real return over 25 years, the multiplier is approximately 4.3. If your retirement target is $1 million and you have 25 years to retirement, your Coast FIRE number is roughly $233,000. If you have $250,000 saved today, you've crossed the Coast FIRE threshold. Your current savings alone, left to grow for 25 years, would reach your target. Any additional contributions accelerate your timeline or increase your final balance.
Crossing the Coast FIRE threshold is a meaningful milestone because it changes the nature of the risk you face. You're no longer dependent on future contributions to reach your target. You still need to not withdraw the money and to maintain a reasonable allocation, but the dependence on future savings rate is removed.
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For deeper context on retirement income strategies, the SEC's investor education site and retirement.gov both provide guidance that complements the numerical analysis. More financial calculators and guides are available through the EvvyTools tools directory and EvvyTools blog.
How Social Security Timing Affects Your Nest Egg Requirement
The decision of when to claim Social Security has a larger effect on retirement outcomes than most people realize. Claiming at 62, the earliest eligibility age, reduces the monthly benefit by 25% to 30% compared to full retirement age. Waiting until 70 increases it by approximately 32% above full retirement age. Both changes are permanent.
For nest egg sizing, this timing decision is directly relevant. Consider a household where claiming at 62 produces $1,800 per month and waiting until 70 produces $2,800 per month. That's $12,000 per year in additional non-portfolio income from delaying. At a 4% withdrawal rate, every $1 of additional annual non-portfolio income reduces the required portfolio size by $25. A $12,000 annual increase in Social Security income reduces the required nest egg by $300,000.
The break-even analysis for Social Security timing works as follows: if you delay from 62 to 70, you give up eight years of reduced benefits. You then need to live long enough to recoup those forgone payments through the higher monthly amount. For most starting points, the break-even age falls around 80 to 82 years. If you live past that age, delaying was the better financial decision.
The Social Security Administration provides personalized benefit estimates based on your earnings record. Using your actual projected benefit at different claiming ages, rather than national averages, produces a more accurate nest egg target. The EvvyTools retirement readiness calculator lets you enter Social Security income as a variable so you can compare scenarios with early versus delayed claiming and see how each affects the required portfolio size.
Running Your Own Numbers
The most important thing to know about retirement readiness analysis is that running the numbers, even with imperfect assumptions, is significantly more useful than not running them. The people who retire without enough money are rarely the ones who calculated it carefully and missed. They're the ones who never ran the numbers at all.
A 30-minute session with a retirement readiness calculator gives you a portfolio target, tells you whether you're ahead or behind, quantifies the gap if one exists, and shows you how sensitive the outcome is to your assumptions. That's enough to make a concrete decision about whether your savings rate needs to change and, if so, by how much.
The specifics change as you get closer to retirement and have better estimates of actual expenses and Social Security benefits. But having a rough picture 20 or 30 years out is far better than operating on intuition alone.
