The single most important question in retirement planning is also the simplest to ask and the hardest to answer: how much money do I actually need?
The good news is that two straightforward rules — the 4% rule and the 25× multiplier — give you a powerful starting point. This guide explains both, shows you how to calculate your personal retirement number, and helps you understand how Social Security, account type, and retirement age change the picture.
RetireMap models your 401k, IRA, Roth IRA, and Social Security together in one free tool.
Open the Free Retirement Calculator →The simplest way to estimate how much you need to retire is to multiply your expected annual retirement spending by 25. This is called your retirement number or FIRE number.
Formula: Retirement Number = Annual Spending × 25
| Annual Spending in Retirement | Retirement Number (25×) |
|---|---|
| $40,000 | $1,000,000 |
| $50,000 | $1,250,000 |
| $60,000 | $1,500,000 |
| $80,000 | $2,000,000 |
| $100,000 | $2,500,000 |
| $120,000 | $3,000,000 |
Important: this is your total portfolio target — meaning the sum across all your accounts (401k, IRA, Roth, brokerage). Social Security reduces how much portfolio you need (more on that below).
The 25× rule comes directly from the 4% safe withdrawal rate, which was established by financial researcher William Bengen in 1994. Bengen analyzed decades of historical stock and bond returns and found that a retiree who withdrew 4% of their portfolio in year one — then adjusted that amount for inflation each year — had a very high probability of not running out of money over a 30-year retirement.
The math: if you need $60,000/year and can withdraw 4%, you need $60,000 ÷ 0.04 = $1,500,000. That's exactly 25× your annual spending.
The 4% rule is a guideline, not a guarantee. It was derived from U.S. historical data and may not hold under all future market conditions. Longer retirements (35–40 years) may warrant a more conservative 3–3.5% withdrawal rate. RetireMap's Monte Carlo simulation runs thousands of market scenarios to show you the probability your portfolio survives to your target age.
Social Security is a guaranteed income stream that reduces how much portfolio you need. Here's how to account for it: subtract your expected annual Social Security benefit from your annual spending target, then apply the 25× rule to the remainder.
Compare that to $70,000 × 25 = $1,750,000 without Social Security. A $24,000 annual SS benefit reduces the portfolio you need by $600,000.
When you claim Social Security matters enormously. Claiming at 62 vs 70 can differ by $12,000–$20,000/year or more. See our guide: Social Security at 62, 67, or 70 — the real numbers.
The 4% rule was designed for a 30-year retirement (retiring at 65, living to 95). If you retire earlier, your portfolio must last longer — which means the safe withdrawal rate is lower and your required savings is higher.
| Retirement Age | Expected Retirement Length | Safer Withdrawal Rate | Multiplier |
|---|---|---|---|
| 70 | ~25 years | 4.5–5% | 20–22× |
| 65 | ~30 years | 4% | 25× |
| 60 | ~35 years | 3.5% | 28–29× |
| 55 | ~40 years | 3% | 33× |
| 50 or earlier | 45+ years | 2.5–3% | 33–40× |
Not all portfolio dollars are worth the same in retirement. A dollar in a Traditional 401k or IRA will be taxed when withdrawn. A dollar in a Roth IRA comes out tax-free. A dollar in a taxable brokerage account is taxed at capital gains rates.
If your $1,500,000 retirement number is all in a Traditional 401k, your effective spendable amount is less — because every withdrawal is ordinary income. Factor in an effective withdrawal tax rate of 15–22% and your real purchasing power may be $1,200,000–$1,275,000.
This is why Roth conversions, tax diversification, and account sequencing matter. RetireMap models your specific account mix so your projection reflects actual after-tax spending power, not just gross balances.
Most Americans are significantly behind standard retirement savings targets at every age. If that describes you, here's where to focus:
Sequence of returns risk: The order in which your investment returns occur matters as much as the average return. A market crash in your first 2–3 years of retirement is far more damaging than the same crash 15 years in. RetireMap's Monte Carlo simulation specifically models this risk.
Your personal retirement number depends on:
The 25× rule is a useful starting point, but it can't account for all of these variables simultaneously. That's what RetireMap is built for.
Enter your accounts, contribution rates, and goals. RetireMap builds a year-by-year projection showing exactly when your portfolio peaks, when it starts drawing down, and whether it lasts to your target age.
Open RetireMap — Free, No Login Required →At a 4% withdrawal rate, $1 million generates $40,000/year. Combined with Social Security of $20,000–$30,000/year, many households can retire comfortably. Whether it's enough depends on your spending needs, retirement age, and location. See our retirement savings benchmarks by age.
Retiring at 55 means your portfolio must last ~40 years. Use a 3% withdrawal rate, which means multiplying your annual spending by 33. If you plan to spend $60,000/year, you'd need about $2 million — before accounting for Social Security (which you won't receive until at least 62).
The original Bengen research covered 30 years. For 40+ year retirements, most financial planners recommend a 3–3.5% withdrawal rate to maintain a high probability of success. RetireMap lets you adjust the withdrawal rate and see the impact in the projection.
Home equity can be a retirement resource (through downsizing or a reverse mortgage), but it's illiquid and complex. Most planners recommend building your investment portfolio target excluding home equity, then treating home equity as a buffer or legacy asset.
This article is for educational and illustrative purposes only. It does not constitute financial, tax, or legal advice. Figures are based on commonly used planning conventions. Consult a qualified financial advisor before making retirement planning decisions.