Your Retirement Number Is Probably Wrong. Here’s Why.

The first time someone explained this to me, I didn’t believe them. A financial planner told me the standard retirement number I’d been working toward—calculated using the popular 80% income replacement rule—was likely off by hundreds of thousands of dollars. Either too high or too low, depending on factors most online calculators don’t even ask about.

I’d spent hours plugging numbers into retirement calculators. They all gave me slightly different answers, but they agreed on the general framework: figure out what you earn now, multiply by 0.8, then use the 4% rule to reverse-engineer how much you need saved. The formula felt scientific. Concrete. Wrong, as it turns out, for most people‘s actual circumstances.

The problem isn’t that these tools are deliberately misleading. It’s that they’re built on averages and assumptions that may have nothing to do with your life. Your retirement number depends on variables most calculators treat as constants.

Why the 80% Rule Breaks Down

The 80% income replacement rule says you’ll need about 80% of your pre-retirement income to maintain your lifestyle once you stop working. The logic seems sound: you’re no longer saving for retirement, commuting to work, or paying payroll taxes, so you need less money.

But here’s what that rule doesn’t account for. If you’re making $100,000 and saving 15% for retirement, you’re actually living on $85,000. Your lifestyle is already based on less than your gross income. Telling you to plan for 80% of gross income—$80,000—means planning for less than you‘re currently spending.

On the flip side, some people will need more than their current income. If your mortgage payment disappears in retirement but you’re planning to travel extensively, or if you’re currently spending nothing on healthcare because your employer covers it, that 80% figure becomes meaningless.

I compared my own numbers. Between retirement contributions, commuting costs, and the mortgage I’ll have paid off, my fixed expenses would drop by about 30%. But healthcare for my spouse and me before Medicare eligibility would add back roughly $1,400 a month. The neat 80% formula didn’t come close to capturing that reality.

What Most Calculators Miss About Healthcare

Healthcare is where retirement number calculations go sideways for almost everyone. Most basic calculators either ignore it completely or use a generic national average that doesn’t reflect individual health situations, medication needs, or geographic location.

Fidelity estimates that a couple retiring at 65 will need about $315,000 saved just for healthcare costs in retirement. That’s separate from your living expenses. And that assumes you’re enrolling in Medicare at 65. If you retire earlier, you’re buying insurance on the private market or through COBRA, which can easily run $1,500 to $2,000 per month for a couple.

Those years between retirement and Medicare eligibility represent a coverage gap that simple retirement calculators handle poorly. They might ask “when do you plan to retire?” but they don’t drill down into what bridging that gap actually costs or how it affects your withdrawal strategy.

Healthcare costs in early retirement can exceed all your other discretionary spending combined. It’s not a line item you can estimate with a percentage.

Do You Actually Spend the Same Amount Every Year?

Most retirement planning assumes your spending stays relatively flat, adjusted for inflation. But research on actual retiree spending shows a different pattern. Spending typically starts higher in early retirement—the “go-go years” when people travel and pursue expensive hobbies—then decreases in later retirement as activity levels naturally decline.

This isn’t universal, of course. Medical expenses can spike dramatically in your eighties and nineties. Long-term care, which Medicare doesn’t cover, averages over $100,000 annually for a private room in a nursing facility. Some people front-load their retirement spending. Others save it for later, whether by choice or necessity.

The point is that your retirement number should probably account for variable spending across different phases, not a single annual figure multiplied by 30 years. A 62-year-old who wants to travel extensively needs a different calculation than someone planning a quiet retirement focused on local activities.

Retirement Phase	Typical Age Range	Spending Pattern
Active/Go-Go Years	60-75	Higher discretionary spending, travel, hobbies
Slow-Go Years	75-85	Moderate spending, less travel, more healthcare
No-Go Years	85+	Lower discretionary, potentially high medical/care costs

How Taxes Change Your Retirement Number

Here’s something that caught me off guard: where your retirement money is saved matters almost as much as how much you’ve saved. Your retirement number looks different depending on whether your savings sit in traditional retirement accounts, Roth accounts, or taxable brokerage accounts.

If you have $1 million in a traditional 401(k), you don’t actually have $1 million to spend. You have $1 million minus whatever you’ll owe in taxes when you withdraw it. At a 22% marginal tax rate, that’s more like $780,000 in spending power. Most basic calculators ask for your total retirement savings but don’t distinguish between pre-tax and after-tax money.

The same million dollars in a Roth IRA is worth the full million because you’ve already paid taxes on those contributions. That difference—$220,000 in this example—is substantial enough to completely change whether you’re on track.

Beyond account type, your retirement number also depends on tax planning during withdrawal. If you’re pulling from Social Security, a pension, traditional IRAs, and taxable accounts simultaneously, the tax treatment of each income stream affects how much you actually keep. Required minimum distributions starting at age 73 can push you into higher tax brackets whether you need the money or not.

What Actually Works Better Than Rules of Thumb

The alternative to generic calculators isn’t necessarily hiring expensive help. It’s doing a more detailed version of the work yourself, based on your actual spending rather than income percentages.

Start with what you spend now, broken down by category. Not what you earn—what actually leaves your accounts each month. Then adjust each category for retirement. The mortgage might disappear. Commuting costs drop to zero. Retirement contributions obviously stop. But healthcare probably increases. Maybe travel increases. Maybe you’re planning to help adult children or grandchildren financially.

This exercise takes longer than plugging three numbers into an online calculator, but it gives you a retirement number based on your actual life, not statistical averages. When I did this, my number shifted by almost 20% compared to what the 80% rule suggested. Lower in some areas, higher in others, but far more accurate to what I’d realistically need.

From there, factor in income sources. Social Security statements show your estimated benefit at different claiming ages. Pensions, if you have one, provide a specific monthly amount. Those reduce how much you need to withdraw from savings each year, which reduces your total retirement number.

The formula gets more complex, yes. But retirement is complex. Pretending it fits neatly into a one-size-fits-all calculator doesn’t make planning easier. It just makes the plan less useful.

I’m skeptical of overly precise projections too. You can’t predict healthcare costs 30 years out or know exactly what your spending habits will be at 75. But you can build a range that accounts for your specific circumstances—your actual housing costs, your health situation, your family obligations—rather than relying on national averages that might bear no resemblance to your reality. That’s not perfect, but it’s honest, and it’s a starting point that won’t mislead you by tens or hundreds of thousands of dollars.

Frequently Asked Questions

How much do I really need for healthcare in early retirement?

For a couple retiring before Medicare eligibility at 65, expect to budget roughly $1,500 to $2,000 per month for health insurance premiums alone on the private market, depending on your state and plan type. That doesn’t include deductibles, copays, or out-of-pocket costs. If you retire at 60 and need five years of coverage before Medicare, you’re looking at $90,000 to $120,000 just in premiums for that gap period.

Should I use my current spending or my income to calculate retirement needs?

Base your retirement number on actual spending, not gross income. If you earn $80,000 but live on $55,000 after taxes, retirement contributions, and other payroll deductions, your lifestyle is built around that $55,000 figure. Starting from income and applying percentage rules often inflates your target unnecessarily or, worse, underestimates it if you have specific upcoming expenses. Track what actually goes out the door each month for the most accurate baseline.

Does the 4% withdrawal rule still work for retirement planning?

The 4% rule—withdrawing 4% of your portfolio in the first year of retirement, then adjusting for inflation—was based on historical data and a 30-year retirement horizon. It’s still a reasonable starting benchmark, but it doesn’t account for sequence of returns risk, longer retirements, or lower expected returns in certain market conditions. Some planners now suggest 3.5% to be more conservative, especially for early retirees who might need their money to last 40 years instead of 30.