How Much Money Do You Really Need to Retire?
The 4% rule says annual spending × 25 = your retirement number. For $60K/yr of spending, that's $1.5M. That single line answers the question for most people. The rest of this guide explains the 5 variables that move the number meaningfully — and the 6 things the FIRE number doesn't tell you.
The honest answer in 60 seconds
Take your annual retirement spending. Multiply by 25. That's your number.
The math behind this comes from the Trinity Study (1998), where researchers at Trinity University ran the historical US stock and bond returns from 1926-1995 against different withdrawal rates and portfolio allocations. The headline finding: a 4% initial withdrawal rate from a 50/50 stock/bond portfolio, increased annually for inflation, succeeded for 30 years in 95%+ of historical rolling periods. 4% withdrawal = 1 / 25 = the multiplier we use.
| Annual spending | FIRE number (× 25) | Conservative (× 33) |
|---|---|---|
| $40,000 | $1.0M | $1.32M |
| $60,000 | $1.5M | $1.98M |
| $80,000 | $2.0M | $2.64M |
| $120,000 | $3.0M | $3.96M |
| $200,000 | $5.0M | $6.60M |
Use × 25 for a standard 30-year retirement at age 65. Use × 33 (a 3% withdrawal rate) if you're retiring before 50, have a 40-50 year retirement horizon, or want extra cushion against sequence-of-returns risk in the early years. We pulled the conservative-rate justification from Wade Pfau's safe-savings-rate research and Morningstar's 2024 State of Retirement Income report, which pegs current safe rates at 3.7% given today's bond yields and equity valuations — meaningfully tighter than the historical 4%.
The 5 variables that actually move your number
Calculators often surface 15-20 variables. In practice, 5 of them move your number by more than ±10%; the rest are rounding error. Here they are in order of impact.
1. Annual spending (impact: 100% — it's the multiplier base)
Every dollar of spending you can cut from your retirement budget cuts your FIRE number by $25. Conversely, every dollar you add costs you $25 of additional portfolio. The asymmetry of compound math means this is the single highest-leverage variable in retirement planning — far more than investment return, far more than savings rate, far more than retirement age.
The honest exercise: pull 12 months of credit card and bank statements, categorize them, and ask which line items will actually disappear or shrink in retirement. Childcare typically drops to zero. Commuting and work clothing drop near zero. Healthcare often increases (more time = more medical care, plus Medicare premiums + gap insurance). Travel typically increases in the first 10 years of retirement, then decreases. Use the Budget Calculator to build the line-item picture.
A useful sanity check: the BLS Consumer Expenditure Survey (2023, latest available) reports the average household aged 65+ spends $52,141/yr, with the bottom quintile at $26K and the top quintile at $108K. If your projected number is wildly outside that range, double-check.
2. Withdrawal rate (impact: ±33% on portfolio size)
Moving from a 4% to a 3% withdrawal rate increases your required portfolio by 33%. The same $60K of spending needs $1.5M at 4% and $2M at 3%. This is more impact than most people realize — and the correct rate depends on three things: retirement length, portfolio allocation, and how much you'll adjust spending in bad market years.
For a 30-year retirement at 65, 4% is reasonable. For a 40-year retirement (early FIRE at 50), use 3.3-3.5%. For 50+ years (FIRE at 40), use 3.0%. The Trinity authors themselves stopped at 30 years; Bengen and Pfau's later work extends to longer horizons.
Alternative: variable withdrawal strategies (Guyton-Klinger, RMD-method, VPW) let you start at 5-5.5% but require cutting spending in bad market years. They're mathematically sound but require behavioral discipline most retirees don't have. The 4% rule's strength is its simplicity — you don't have to make decisions in panic moments.
3. Expected real return (impact: ±20% on accumulation timeline)
'Real return' = nominal return minus inflation. A 100% US stock portfolio has averaged 6.5-7% real over the past century per the Shiller dataset. A 60/40 stock/bond mix averages closer to 5%. Treasury-only retirement portfolios run 1-2% real.
This variable matters more for the accumulation timeline (how many years until you hit your number) than for the number itself. At 7% real, saving $20K/yr for 30 years gets you to $2M. At 5% real, the same saving rate gets you to $1.4M — a 30% gap purely from return assumption.
Honest assumption-setting: use 5% real for planning. It builds in a margin against forward-looking expected returns being lower than backward-looking historical returns — a real possibility given current equity valuations (Shiller CAPE ~32 vs historical median ~16) and bond yields. Run the Compound Interest Calculator with both 5% and 7% to see your range.
4. Years in retirement (impact: ±15% on safe rate)
A 50-year retirement (FIRE at 40) is fundamentally different math than a 25-year retirement (traditional retirement at 65, life expectancy ~85). Longer retirement = more sequences of returns to weather = lower sustainable withdrawal rate.
SSA life expectancy tables (2024) show a 65-year-old can expect to live to ~84 (men) or ~87 (women). A 65-year-old couple has roughly a 50% chance that at least one spouse lives past 92. Plan retirement length as max(spouse 1 expectancy + 5 years, spouse 2 expectancy + 5 years) — not the average.
5. Other income (Social Security, pensions, part-time work)
Income that's not from your portfolio reduces your required portfolio dollar-for-dollar against your spending. The math: required portfolio = (annual spending − other annual income) × 25.
For Social Security, the average 2025 benefit is $1,976/month ($23,712/yr), with the maximum at full retirement age around $4,018/month ($48,216/yr). A married couple where both spouses worked typically receives a combined $40K-$70K/yr — which can reduce a $1.5M-needed portfolio to $500K-$800K. See the Social Security Claim Age tool for your specific projection.
Important: only count income that's inflation-adjusted (Social Security is, COLA-indexed; most private pensions are not). For non-inflation-adjusted income, model a real-value decline of ~25% over 30 years at 2% inflation, or ~45% at 3% inflation.
Run YOUR specific number, not the median
Every retirement is a single observation, not a distribution. The median 65-year-old retiring with $1.5M is a useful reference point and a useless basis for your specific decision. Your spending pattern, your spouse's working status, your healthcare costs, your kids' financial trajectories, your housing situation — all of them push your number around by ±20-40% from the median.
The minimum useful exercise: open the FIRE Calculator, plug in your real numbers (not round defaults), and look at the Monte Carlo distribution — not the single-point estimate. The 10th percentile outcome is your downside scenario; the 50th is what people quote; the 90th is what your social media feed shows you. Plan for the 25th percentile, hope for the 50th, treat the 75th as gravy.
Open the FIRE Calculator →6 things the FIRE number doesn't tell you
Hitting your number is necessary but not sufficient. Six things can derail an on-paper-adequate retirement.
1. Sequence of returns risk
Two retirees with identical average returns can end up wildly different if one hits a bear market in year 1 versus year 20. Withdrawing 4% during a 30% drawdown depletes the portfolio faster than the recovery can rebuild. Per Wade Pfau's analysis, retirees who started in 1966 (just before the bear market) ran out at much lower withdrawal rates than retirees who started in 1982 (just before the bull market) — same headline average returns, dramatically different outcomes. Mitigation: hold 2-3 years of expenses in cash/short-bonds at retirement, refill from equities only in years they're up. The FIRE Calculator's Monte Carlo mode shows this risk explicitly via the 10th-percentile outcome.
2. Healthcare costs scale faster than inflation
Per Fidelity's 2024 Retiree Health Care Cost Estimate, a 65-year-old couple retiring today needs about $315,000 set aside for healthcare costs over a 20-year retirement — and that's after Medicare. Long-term care is separate and can run $100K-$200K/yr at the high end. Healthcare inflation has averaged ~4.5% over the past 20 years vs CPI ~3% (CMS National Health Expenditure data). If you're modeling at CPI inflation, your healthcare line item is mis-estimated. Use the Healthcare Cost Estimator to scope this.
3. Social Security timing is a $200K+ lifetime decision
Claiming at 62 vs 70 swings the lifetime present value of benefits by $200K-$400K for typical-earner couples per SSA's actuarial data. The optimal claim age depends on health, marital status, other income sources, and tax bracket — not just life expectancy. The default "claim ASAP" instinct is usually wrong for the higher-earning spouse in a couple. Model your specific case in the Social Security Claim Age tool.
4. Tax-aware withdrawal can save $300K+ over retirement
Standard advice — "spend taxable accounts first, then Traditional, then Roth" — minimizes early-retirement taxes but maximizes lifetime taxes for most retirees. The reason: it leaves you with a giant Traditional balance that gets force-distributed at age 73 via RMDs, often spiking you into higher brackets and triggering IRMAA Medicare surcharges. Better strategy: every year between retirement and Social Security claim age (the "bracket gap"), do Roth conversions to fill the 10-12-22% brackets. Most early retirees can convert $100K-$300K of Traditional to Roth at low rates during this window, saving themselves much more in future taxes. Model it in the Roth Conversion tool.
5. Long-term care is the giant tail risk
Per HHS data, ~70% of 65-year-olds will need some form of long-term care in their lifetime, and ~20% will need it for 5+ years. Costs run $60K-$120K/yr for assisted living, $90K-$160K/yr for nursing homes. Medicare does NOT cover long-term care; Medicaid does but requires spending down assets first. Options: long-term care insurance (expensive, premiums often rise), hybrid life-insurance + LTC policies, self-insuring (need ~$300K-$500K extra), or planned Medicaid spend-down (politically uncertain). Most retirement calculators ignore this entirely. At minimum, plan as if there's a 30% chance one spouse will incur $300K+ in care costs.
6. Inflation is personal, not CPI
Your personal inflation rate depends on your basket. Retirees skew heavily toward healthcare (running 4.5% inflation), insurance (3-4%), property taxes (variable, often 3-5%), and energy (volatile). They skew away from technology and apparel (often deflationary). The result: most retirees experience 1-2 percentage points above CPI in lived inflation. Use the Personal Inflation tool to estimate your specific basket, then add 0.5-1pt to your assumed inflation rate in retirement modeling.
Frequently asked questions
What to actually do this month, this year, this decade
- Run your specific number in the FIRE Calculator. Use real spending (pull 12 months of statements), not what feels right.
- Check whether you're maxing tax-advantaged accounts. 2025 limits: $23,000 401(k), $7,000 IRA, $4,300/$8,550 HSA (single/family).
- Save a snapshot. The point of WhatIf Labo's snapshot system is to make 6-months-from-now you able to see what changed.
- Audit your asset allocation. Most US-domiciled retirees benefit from 60/40 or 70/30 stock/bond in retirement, more equity in accumulation.
- Build the bracket-gap plan. Map your expected income each year from retirement to Social Security claim age. The low-income years are your tax-strategy window.
- Model healthcare-cost scenarios. If you're retiring before 65, get a real ACA quote based on your projected AGI, not a vague "I'll figure it out".
- Optimize the savings rate, not the returns. A 1% increase in savings rate moves the retirement date more than chasing returns.
- Plan for housing decisions before age 60. Sell-and-downsize works best when planned; reverse-mortgage and home-equity-as-retirement-savings are usually worse than they sound.
- Build the snapshot habit. Save a financial snapshot every 6 months. By retirement, you'll have 20 years of data showing what actually moved the number — and what didn't.