How Much Do I Need to Retire? A Data-Driven Answer

It is the most common question in personal finance: “How much money do I need to retire?” The internet is full of answers — $1 million, $2 million, 25 times your annual spending — but most of them are dangerously oversimplified. The real answer depends on your spending, your timeline, your other income sources, and your tolerance for risk.

Let's walk through how to actually figure this out, starting with the common rules of thumb and ending with a more rigorous, data-driven approach.

The Rules of Thumb (and Why They Fall Short)

You've probably encountered these guidelines:

• 25x annual spending — the inverse of the 4% rule. If you spend $60,000 per year, you need $1.5 million.
• Round-number targets — “I need $1 million” or “I need $2 million.” These are psychologically satisfying but have no connection to your actual spending.
• The 80% replacement rate — financial advisors often suggest you need 80% of your pre-retirement income. If you earned $100,000, plan for $80,000 in retirement spending.

These are fine as starting points, but each has serious limitations. The 25x rule assumes a 30-year retirement, a specific asset allocation, and historical U.S. market returns. The round-number targets are arbitrary. And the 80% replacement rate conflates income with spending — if you were saving 30% of your income, you were already living on 70%, so 80% of income is actually more than you were spending while working.

The deeper problem is that all of these give you a single number with false precision. Retirement planning is not that clean.

Start with Spending, Not Income

The right question is not “how much do I need?” but “how much will I spend?” Your retirement number is a function of your spending, so that is where the analysis has to begin.

Many retirees spend less than they did during their working years. The commute disappears. Work clothes become optional. The mortgage may be paid off. Payroll taxes vanish. Retirement contributions stop. For some people, actual spending in retirement drops 20–30% below their working-years budget.

But others spend more. The early years of retirement often involve travel, hobbies, and deferred projects. Healthcare costs can rise significantly, especially before Medicare eligibility at 65. And some retirees simply underestimate how much they will spend when every day is a Saturday.

The honest approach is to build a bottom-up spending estimate. Track your current expenses, remove work-related costs, add retirement-specific costs (healthcare, travel, hobbies), and arrive at a realistic annual figure. A budgeting tool like Monarch Money can help you build that picture. This is your baseline. If you want to calculate your FIRE number precisely, this step is non-negotiable.

The Multiplier Depends on Your Timeline

The 25x rule comes from the Trinity Study, which tested a 30-year retirement period. That works well for someone retiring at 65 who expects to live to 95. But timelines vary enormously:

Someone pursuing FIRE at 35 needs their portfolio to last 50 or more years. Over that horizon, the original 4% rule's historical success rate drops noticeably. You either need a larger portfolio (a lower withdrawal rate, say 3.25–3.5%), or you need to adopt a dynamic withdrawal strategy that adjusts spending based on portfolio performance.

Conversely, someone retiring at 65 with Social Security starting at 67 may find that 20–22x of their gap spending (the amount not covered by Social Security) is more than sufficient.

Other Income Changes Everything

This is the single most common mistake in “how much do I need” calculations: ignoring other income sources.

Your portfolio does not need to fund your entire retirement. It only needs to cover the gap between your spending and your other guaranteed income. Consider:

• Social Security — the average benefit is roughly $22,000 per year; a high earner delaying to 70 might receive $45,000 or more. For a couple, combined benefits can easily exceed $50,000.
• Pensions — increasingly rare in the private sector, but still common for government employees, teachers, and military retirees.
• Rental income — if you own income-producing property, the net cash flow reduces the portfolio burden.
• Part-time work — even modest income in the first few years of retirement dramatically reduces sequence-of-returns risk by lowering the amount withdrawn from the portfolio during the most vulnerable early period.

Here is a concrete example. Suppose you expect to spend $60,000 per year in retirement. If Social Security provides $25,000, your portfolio only needs to generate $35,000 per year. At the 4% rule, that requires $875,000 — not $1.5 million. The difference is enormous.

Of course, Social Security may not start immediately. If you retire at 55 but don't claim until 67, your portfolio needs to cover the full $60,000 for those 12 bridge years. This is where detailed planning and simulation become essential.

Healthcare: The Wildcard

Healthcare is the expense that derails more retirement plans than market crashes. The challenge differs dramatically based on age:

Before 65 (pre-Medicare): If you retire before Medicare eligibility, you need to purchase health insurance on the ACA marketplace or through COBRA (temporarily). Premiums for a couple in their 50s can run $1,500–$2,500 per month before subsidies. ACA subsidies are based on Modified Adjusted Gross Income (MAGI), which creates a planning opportunity: by managing Roth conversions, capital gains, and portfolio withdrawals, early retirees can often keep MAGI low enough to qualify for substantial premium subsidies. But this requires careful tax planning.

After 65 (Medicare): Medicare covers most major medical expenses, but it is not free. Between Part B premiums, Part D (prescription drug coverage), Medigap or Medicare Advantage premiums, and out-of-pocket costs, a retiree should budget $3,000–$7,000 per person per year, depending on health status and coverage choices. Long-term care is an additional risk that Medicare does not cover.

The upshot: if you are retiring before 65, add $15,000–$30,000 per year to your spending estimate for healthcare (for a couple), unless you have a clear plan for subsidized coverage. This alone can add $375,000–$750,000 to your target number at the 25x multiplier.

Why a Single Number Is the Wrong Answer

After reading all of the above, you might be tempted to plug in your numbers and arrive at a single target: “I need $1.47 million.” Resist that temptation.

A single number implies certainty that does not exist. Markets fluctuate. Inflation is unpredictable. Your spending will change. Your health will change. The economy will do things no historical data predicted.

The better way to think about retirement readiness is probabilistic. Instead of “I need $1.5 million,” the real answer sounds more like this:

“With $1.5 million, spending $55,000 per year with Social Security starting at 67, and a 70/30 stock/bond allocation, I have a 92% historical success rate over a 35-year retirement.”

That 92% is not a guarantee — it means that in 92% of all historical 35-year periods, your money would have lasted. It also means in 8% of periods, it would not have. That context is far more useful than a single number because it lets you make informed decisions:

• Is 92% comfortable enough? If not, save more, spend less, or plan to work a bit longer.
• What happens if you reduce spending by $5,000/year? The success rate might jump to 97%.
• What if you adopt a flexible withdrawal strategy that cuts spending in bad markets? You might maintain a 95%+ success rate with a smaller portfolio.

This is why simulation matters. Arithmetic gives you a target. Simulation gives you a probability distribution — and the confidence to actually act on it.

Putting It All Together

Here is a practical framework for determining how much you need to retire:

1. Estimate your annual spending in retirement. Be honest and specific. Build it from the bottom up, not the top down.
2. Subtract guaranteed income. Social Security, pensions, annuities, rental income. The remainder is what your portfolio must fund.
3. Account for healthcare. If retiring before 65, budget explicitly for premiums and out-of-pocket costs. Do not assume your working-years employer plan costs will carry over.
4. Choose a timeline. Plan to at least age 95. If you are retiring early, plan longer. Running out of money at 89 is not a theoretical problem — it is a devastating one.
5. Run a simulation. Use historical or Monte Carlo simulation to test your plan across hundreds of market scenarios. Look at the success rate, the worst-case outcomes, and the sequence-of-returns risk in early retirement years.
6. Adjust and iterate. Tweak spending, retirement age, asset allocation, and withdrawal strategy until you find a plan that balances your goals with an acceptable level of risk.

Run Your Numbers

Rules of thumb can start a conversation, but they cannot finish one. Your retirement is too important to leave to rough arithmetic and round numbers.

Use the FIREwiz Retirement Simulator to model your specific situation, or track your progress toward your target with a free tool like Empower. Input your spending, your assets, your expected Social Security income, and your preferred withdrawal strategy. The simulator will run your plan against decades of historical market data and show you not just whether your money will last — but how confident you can be that it will.

If you are still in the saving phase, the Accumulation Calculator can help you figure out how long it will take to reach your target given your current savings rate and asset allocation.

The question is not “how much do I need to retire?” The question is “how confident am I that my plan will work?” That is a question only simulation can answer.