Retirement Calculator: How Much Do You Need?
Most people guess their retirement number. A calculator does it properly: estimate annual spending, multiply by ~25, and check whether your savings rate gets you there.
Don't have time? Here's what you need to know:
- 1The 4% rule implies a target of roughly 25× your annual portfolio spending — $50k/year needs about $1.25M.
- 2Subtract Social Security and pensions first; your portfolio only has to cover the remaining spending gap.
- 3Early retirees and conservative portfolios should plan around 3.25%–3.5% withdrawals, meaning a larger nest egg.
- 4Plan in real dollars: at 3% inflation, a $50k lifestyle costs about $90k in 20 years.
Your Retirement Number Starts With Spending, Not Savings
A retirement calculator flips the usual question. Instead of asking how big your savings might grow, it asks how much you'll spend in retirement and then works backward to the nest egg that can fund it. The anchor is your expected annual spending, because a portfolio's job is to replace your paycheck — and the size of paycheck you need is what sets the target.
The most common shortcut is the 4% rule, derived from the Trinity Study and William Bengen's research on sustainable withdrawal rates. It says that if you withdraw about 4% of your portfolio in the first year of retirement and adjust for inflation thereafter, the money has historically lasted at least 30 years across a wide range of market conditions. Flip 4% around and you get a simple target: roughly 25 times your annual spending.
Worked Example: $50,000 a Year Needs ~$1.25 Million
Suppose you expect to spend $50,000 a year in retirement, on top of any Social Security or pension. Multiply by 25 and your target is about $1.25 million. If you expect $20,000 a year from Social Security, your portfolio only needs to cover the remaining $30,000, which lowers the target to roughly $750,000 — a reminder that the calculator's inputs change the answer dramatically.
The next step is checking whether your savings rate reaches that number in time. Starting from $200,000 with 20 years left and a 7% real return, contributing about $1,500 a month gets you close to $1.25 million. The table shows how the target scales with spending — and why trimming planned expenses is one of the most powerful levers in the whole calculation.
| Annual spending need | × 25 (4% rule) | Target portfolio |
|---|---|---|
| $30,000 | 25 | ~$750,000 |
| $50,000 | 25 | ~$1,250,000 |
| $70,000 | 25 | ~$1,750,000 |
| $100,000 | 25 | ~$2,500,000 |
Tip: Subtract guaranteed income (Social Security, pensions) from your spending before multiplying by 25. Your portfolio only needs to cover the gap, not your entire budget.
Where the 4% Rule Gets Fuzzy
The 4% rule is a useful starting point, not a law. It was built on U.S. market history and a 30-year retirement; if you retire early and need the money to last 40 or 50 years, a more conservative 3.25% to 3.5% withdrawal rate is often suggested, which raises your target toward 28–30 times spending. Retire later with a shorter horizon and you can arguably withdraw a bit more.
The rule also assumes a stock-heavy portfolio — typically something like 50–75% stocks — to outpace inflation over decades. A very conservative all-bond portfolio historically couldn't sustain 4% safely. And it ignores sequence-of-returns risk: a deep market crash in your first few retirement years is far more damaging than the same crash later, because you're selling shares while they're cheap. A good calculator or a flexible spending plan accounts for that.
Important: Don't treat 4% as guaranteed. Early retirees and conservative portfolios should plan around a lower withdrawal rate, which means a larger nest egg than 25x.
Want the full framework? This 2-hour ETF course teaches you exactly how to pick, buy, and hold profitable ETFs — from zero to confident investor. Under $15.
Inflation Is the Silent Variable
Retirement spans decades, and inflation compounds against you the entire time. At 3% inflation, the $50,000 lifestyle you plan for today costs about $90,000 in 20 years and $120,000 in 30. A retirement calculator that ignores inflation will badly understate the number you need, which is why you should plan in real (inflation-adjusted) terms throughout.
Practically, that means using a real return of around 7% for stocks (or roughly 5% for a balanced mix) when projecting growth, and treating your spending target as today's dollars that the 4% rule already inflation-adjusts each year. The whole point of holding growth-oriented ETFs rather than cash in retirement is to keep your withdrawals rising with prices instead of eroding.
Turning the Target Into a Contribution Plan
Once you have a target, the calculator's most useful job is solving for the monthly contribution that reaches it given your current balance, years remaining, and expected return. That number — not the headline nest egg — is what you act on. If it's uncomfortably large, you have three levers: save more, work a bit longer, or plan to spend less in retirement.
On the investment side, retirement portfolios usually pair broad stock ETFs for growth with bond ETFs for stability, shifting more conservative as you approach the date. Model the math with the ETF return calculator, and use the portfolio wizard to set an age-appropriate stock-bond split.
Frequently Asked Questions
How does the 4% rule decide how much I need to retire?
The 4% rule says a portfolio can sustain inflation-adjusted withdrawals of about 4% per year for at least 30 years. Inverting that, you need roughly 25 times your annual spending. If you'll spend $50,000 a year from your portfolio, the target is about $1.25 million.
Should early retirees use a withdrawal rate lower than 4%?
Generally yes. The 4% rule was tested over 30-year retirements. If you retire early and need 40–50 years of income, many planners suggest 3.25%–3.5% to be safe, which raises your target to roughly 28–30 times annual spending instead of 25.
Does the retirement number include Social Security?
It shouldn't be double-counted. Subtract expected Social Security and any pension income from your annual spending first, then apply the 25x multiple to the remaining gap. Guaranteed income reduces how much your portfolio has to cover, lowering your target substantially.
How do I account for inflation in a retirement projection?
Plan in today's dollars and use real (inflation-adjusted) returns — about 7% for stocks or 5% for a balanced portfolio. The 4% rule already builds in annual inflation adjustments to withdrawals, so your spending target represents today's purchasing power, not a fixed future dollar amount.
Further Reading
Free Tools
Alex Harrington
CFA Level II Candidate, Finance & Economics
Alex Harrington is an independent ETF researcher and personal finance writer with over 8 years of experience analyzing exchange-traded funds. A CFA Level II candidate with a background in economics, Alex has reviewed 800+ ETFs and helped thousands of beginners build their first investment portfolios through clear, jargon-free education.
This content is for educational purposes only and does not constitute financial advice. Past performance does not guarantee future results. Consult a licensed financial advisor before making investment decisions.