How Much Do You Actually Need to Retire? (The Calculation Most People Get Wrong)
"Retire with a million dollars." This figure has been circulating in personal finance conversations for decades, at this point almost as a cultural shorthand for financial…
"Retire with a million dollars." This figure has been circulating in personal finance conversations for decades, at this point almost as a cultural shorthand for financial success. Save enough to hit seven figures and you're set.
The problem is that whether a million dollars is enough to retire on depends on a fairly long list of variables that the round number doesn't account for — variables like your annual spending in retirement, where you live, your health situation, whether you'll have other income sources, and when you plan to retire. For some people, a million dollars is more than enough. For others, it's significantly short. For a growing number of people in high-cost cities, it's the wrong order of magnitude entirely.
Getting the retirement number right — your number, not a cultural shorthand — is one of the more important financial calculations you'll ever do. Here's how to actually approach it.
The foundation: the 4% rule and what it actually means
The most commonly cited retirement calculation framework is the 4% rule, which says that you can safely withdraw 4% of your retirement portfolio in the first year and adjust for inflation each year thereafter, with a high probability of not outliving your money over a 30-year retirement.
The 4% rule comes from research by financial advisors William Bengen and the so-called "Trinity Study" in the 1990s. It was based on historical US market returns and was designed to give retirees a high probability of portfolio survival over 30 years.
Applying the rule backward gives you your retirement number:
If you plan to spend $60,000 per year in retirement, you need $1.5 million.
If you plan to spend $40,000 per year, you need $1 million.
If you plan to spend $80,000 per year, you need $2 million.
The rule provides a simple, mathematically grounded starting point. And it immediately illustrates why "a million dollars" is an incomplete answer — it assumes $40,000 of annual spending, which covers very different lives in very different places.
Why most people get this calculation wrong
They use their current spending rather than their projected retirement spending. Your retirement spending will not look like your working-life spending. Some costs go down: commuting, professional clothing, work lunches, potentially childcare. Some go up: healthcare, travel, leisure, potentially housing if you've downsized or relocated. Healthcare is typically the most significant upward adjustment — medical costs in retirement tend to be 2–3x higher than during working years, and long-term care expenses can be substantially higher still.
They don't account for other income sources. Social Security benefits, pension income, part-time work income, rental income — any guaranteed or likely income source in retirement reduces the amount your portfolio needs to generate. If you'll receive $24,000 per year from Social Security and you need $60,000 total, your portfolio only needs to cover the $36,000 gap, which means a portfolio of $900,000 rather than $1.5 million.
They don't adjust for retirement age. The 4% rule is calibrated for a 30-year retirement, which assumes a retirement age of roughly 65. If you plan to retire at 55, you might need a 40+ year portfolio horizon, which calls for a more conservative withdrawal rate — some financial planners suggest 3% to 3.5% for extended retirements. If you plan to retire at 70, the 30-year horizon is shorter, potentially allowing a higher withdrawal rate.
They don't account for inflation. A 3% annual inflation rate cuts purchasing power roughly in half over 24 years. The $60,000 you plan to spend in retirement's first year will cost effectively $120,000 in inflation-adjusted terms by year 24, which the 4% framework partially addresses through its inflation-adjustment mechanism, but which needs to be understood when projecting savings targets and investment returns.
Building your actual retirement number
Here's the process that produces an honest, personalised figure.
Step 1: Estimate your annual retirement spending.
Start with your current essential spending — what you actually spend on necessities today. Then adjust category by category:
Housing: will you own outright (lower cost), rent (variable), or have a mortgage? Factor in property taxes, insurance, and maintenance if you own.
Healthcare: add $5,000 to $15,000 per year per person for medical expenses, depending on your health history and the coverage you expect. Long-term care insurance or self-funding for potential care needs should be addressed separately.
Transportation: most retirees spend less here, though some spend more if they travel more.
Food: often slightly lower as you cook more and buy in bulk.
Add up the adjusted figure. This is your baseline annual retirement spending estimate.
Step 2: Identify other income sources.
Calculate your expected Social Security benefit at your planned retirement age (SSA.gov provides a personalised estimate through your account). Add any pension income, rental income, part-time work income, or other guaranteed sources.
Subtract total guaranteed income from your annual spending estimate. The remainder is what your portfolio must fund.
Step 3: Apply the withdrawal rate.
Divide the portfolio-funded amount by your planned withdrawal rate: 4% for standard retirements, 3–3.5% for early retirements, potentially 4.5–5% for very late retirements with shorter horizons.
This is more precise than "a million dollars" — and it's built from your actual spending patterns and income expectations rather than a round number.
Step 4: Calculate how much you need to save each month.
With a target and a timeline, the monthly savings requirement follows:
Use a future value calculation or a financial planning tool to determine what monthly contribution at your expected investment return rate will produce your target portfolio by your retirement date.
Cashowa's financial planner runs this calculation from your specific inputs — current savings, expected retirement date, portfolio target, and assumed return — and produces a month-by-month projection showing whether you're on track and what adjustments would change the trajectory. Every figure in the projection is computed from your inputs and displayed with the calculation visible.
The variables you should stress-test
No retirement projection is certain. The inputs are estimates, and the future is unknown. The response isn't to avoid the calculation — it's to understand how sensitive your number is to changes in the key assumptions.
Investment return. The 4% rule assumes a portfolio of roughly 60% stocks and 40% bonds with historical average returns. If actual returns are lower — as some analysts argue they may be for the next decade — a lower withdrawal rate is prudent. Running the calculation at 3.5% rather than 4% tells you how much more buffer you'd want.
Healthcare costs. These are the most unpredictable and potentially the most expensive variable in a retirement plan. Running your calculation with a high-healthcare scenario — particularly if there's family history of significant medical needs — is prudent.
Longevity. A 30-year retirement horizon was calibrated for a 65-year-old with average life expectancy. People in good health routinely live to 90 and beyond. Running the calculation for a 35-year horizon rather than 30 is a simple stress test.
Inflation. 3% long-term inflation is the standard assumption. Periods of higher inflation, as many people experienced in the early 2020s, can materially affect purchasing power. A higher inflation assumption in the stress test builds in additional buffer.
Frequently asked questions
Is the 4% rule still valid?
It's contested. Some researchers argue that current market valuations and lower expected future returns make 4% too aggressive for new retirees; they suggest 3–3.5% as a safer withdrawal rate. Others argue the rule remains valid. The practical response is to treat 4% as a starting estimate and err on the side of saving more rather than less, particularly if you have significant retirement years ahead.
What if I don't expect to have Social Security?
If you're outside the US or genuinely don't expect to receive Social Security, your portfolio needs to fund the full retirement spending amount. This increases the required portfolio by the capitalised value of what Social Security would have provided. For example, if you're losing $24,000 per year in expected Social Security income and using a 4% withdrawal rate, the additional portfolio required is $600,000.
Should I include my home equity in my retirement number?
Possibly, but carefully. Home equity is illiquid unless you sell, downsize, or use a reverse mortgage. If you're planning to downsize in retirement and convert equity to investable assets, include the proceeds in your projection. If you're planning to stay in the home, don't include it in your portfolio projection — it's not generating income or available to fund spending.
For most people in the accumulation phase (20+ years from retirement), a high equity allocation — 80–90% stocks — captures the growth potential that long time horizons allow. As retirement approaches, shifting toward a more balanced allocation (60% stocks, 40% bonds) reduces volatility risk. In retirement, the conventional guidance is a 40–60% equity allocation depending on your time horizon and risk tolerance.
What if I save less than I need? Am I just stuck?
A retirement savings shortfall has several potential responses: work a few years longer (significantly extends the portfolio and reduces the withdrawal period), reduce planned retirement spending, take on part-time work in retirement, or accept a higher withdrawal rate (with a higher risk of portfolio depletion). None of these are ideal, but they're real options. The earlier you know about a shortfall, the more options you have.
How do taxes affect my retirement number?
Significantly, and in a way most people don't account for accurately. Traditional IRA and 401(k) withdrawals are taxed as ordinary income in retirement. Roth IRA withdrawals are tax-free. Your Social Security benefit may be partially taxable depending on your total income. Running your retirement number without accounting for taxes overstates how far your portfolio goes. Including a realistic effective tax rate in the spending estimate — or planning to draw primarily from Roth accounts to manage the tax liability — produces a more accurate picture.