For a step-by-step framework on calculating your retirement number, see the How Much to Retire hub.
The 4% rule is the most cited withdrawal guideline in retirement planning — but it was calculated under specific assumptions that may or may not match your situation, and current research actively debates the right number. Here is how to think about withdrawal rates scientifically.
How Safe Withdrawal Rates Are Calculated
Safe withdrawal rate research uses historical portfolio data (Monte Carlo simulations, historical sequence testing, or forward-looking capital market assumptions) to find the maximum percentage that would have survived — or is projected to survive — a target retirement length.
| Method | Description | Limitations |
|---|---|---|
| Historical sequence testing | Test actual sequences of 30-year returns from 1926-present | Past results; future may differ |
| Monte Carlo simulation | Run thousands of random scenarios using historical distributions | Statistical, not guaranteed |
| Forward-looking capital market assumptions | Project future returns from current valuations and yields, rather than historical averages | Depends heavily on the assumptions used |
| “Floor + upside” models | Separate guaranteed income from portfolio withdrawals | More nuanced; harder to model |
The original Bengen study found 4.1% was the maximum rate that survived every 30-year period from 1926-1992 with a 50/50 portfolio.
What the Current Research Says
There is no consensus “safe” number — researchers using different methodologies land in different places, and the range has genuinely widened as of 2026:
| Study / Source | Recommended SWR | Key Finding |
|---|---|---|
| Bengen (1994) | 4.1% | Original “4% rule” with 50/50 portfolio, 30 years, historical backtest |
| Trinity Study (1998) | ~4% | High success rate over 30 years, historical backtest |
| Morningstar (2025) | 3.7% | Forward-looking capital market assumptions; lower starting yields reduce sustainable rates |
| Morningstar (2026) | 3.9% | Updated forward-looking estimate; modestly improved capital market assumptions vs. 2025 |
| Bengen (2025 update) | 4.7% (worst-case historical), 5.25-5.5% (“reasonable conservative”) | Uses a more globally diversified portfolio (adds mid-cap, small-cap, international equities) |
| Kitces (ongoing research) | 4%+ with flexibility | Guardrails approach enables higher rates |
| Wade Pfau | Roughly 2.9-3.4% in some analyses | For 30-40 year retirements in lower-yield environments |
The takeaway: As of 2026, credible researchers span roughly 3.7% to 5.5% depending on methodology (forward-looking vs. historical), portfolio diversification, and time horizon. There is no single “correct” answer — treat 4% as a reasonable starting point to stress-test against your own flexibility and guaranteed income, not as a guarantee.
Safe Withdrawal Rate by Retirement Length
| Retirement Length | Conservative SWR | Moderate SWR | Aggressive SWR |
|---|---|---|---|
| 40 years (retire at 55) | 3.0% | 3.3% | 3.7% |
| 35 years (retire at 60) | 3.3% | 3.6% | 4.0% |
| 30 years (retire at 65) | 3.5% | 4.0% | 4.5% |
| 25 years (retire at 70) | 4.0% | 4.5% | 5.0% |
| 20 years (retire at 75) | 4.5% | 5.0% | 5.5% |
Conservative = historically very high success rate. Moderate = historically high success rate. Aggressive = historically moderate success rate. Based on historical US data — treat as illustrative ranges, not guarantees.
Safe Withdrawal Rate by Asset Allocation
| Stock / Bond Allocation | 30-Year SWR (Moderate success, historical) |
|---|---|
| 20% stocks / 80% bonds | 3.2% |
| 30% stocks / 70% bonds | 3.5% |
| 40% stocks / 60% bonds | 3.7% |
| 50% stocks / 50% bonds | 4.0% |
| 60% stocks / 40% bonds | 4.1% |
| 70% stocks / 30% bonds | 4.1% |
| 80% stocks / 20% bonds | 4.0% (higher volatility) |
| 100% stocks | 3.8% (higher sequence risk) |
Key finding: An all-bond portfolio is not “safe” — it fails to grow against inflation. A moderate stock allocation (50-70%) actually improves withdrawal sustainability while adding short-term volatility.
Fixed vs. Dynamic Withdrawal Strategies
Most research on the “4% rule” assumes fixed withdrawals — you take the same inflation-adjusted amount each year regardless of market performance. This is simple but suboptimal.
Fixed Withdrawal (Traditional 4% Rule)
| Year | Withdrawal | Portfolio Value | Notes |
|---|---|---|---|
| Year 1 | $40,000 (4% of $1M) | $1,000,000 | Baseline |
| Year 5 | $44,000 (inflation-adjusted) | $850,000 after market drop | Still taking $44K |
| Year 10 | $49,000 | $920,000 recovered | Portfolio damaged by early withdrawals |
Risk: If markets drop early, you continue withdrawing the same amount, accelerating depletion.
The Guardrails Approach (Dynamic Withdrawal)
Developed by Jonathan Guyton and William Klinger. Withdraw flexibly based on portfolio performance:
| Condition | Action |
|---|---|
| Portfolio withdrawal rate exceeds 5.4% (upper guardrail) | Reduce spending by 10% |
| Portfolio withdrawal rate drops below 3.4% (lower guardrail) | Increase spending by 10% |
| Normal corridor (3.4%-5.4%) | Continue inflation-adjusted withdrawal |
Result: Guardrails allow a starting withdrawal rate of 4.5-5.5% with a comparable long-term success probability to a fixed 4% rule, in many historical backtests.
RMD-Based Withdrawal Strategy
The IRS Required Minimum Distribution formula divides your balance by a life expectancy factor each year. This naturally reduces withdrawals in bad markets (lower balance = lower withdrawal) and increases them when portfolio grows.
| Age | RMD Life Expectancy Factor | $1M Portfolio → Withdrawal |
|---|---|---|
| 73 | 26.5 | $37,736 (3.77%) |
| 75 | 24.6 | $40,650 (4.07%) |
| 80 | 20.2 | $49,505 (4.95%) |
| 85 | 16.0 | $62,500 (6.25%) |
| 90 | 12.2 | $81,967 (8.2%) |
This is inherently a decreasing-real-spending approach — useful for older retirees.
What Factors Increase Your Sustainable Rate
| Factor | Directional Impact on Sustainable Withdrawal Rate |
|---|---|
| Social Security covers most essential expenses | Meaningfully higher — less portfolio dependence |
| Spending flexibility (can reduce by 10% in bad years) | Meaningfully higher |
| Shorter retirement horizon (age 70+) | Higher |
| Part-time income in early retirement years | Higher |
| Paid-off housing (no rent/mortgage in expenses) | Somewhat higher |
| Significant legacy desire (must leave assets) | Lower |
| Very long expected retirement (40+ years) | Lower |
| High current stock valuations | Lower, per some forward-looking models |
Income from a Portfolio at Various Withdrawal Rates
| Portfolio Size | 3% | 3.5% | 4% | 4.5% | 5% |
|---|---|---|---|---|---|
| $500,000 | $15,000 | $17,500 | $20,000 | $22,500 | $25,000 |
| $750,000 | $22,500 | $26,250 | $30,000 | $33,750 | $37,500 |
| $1,000,000 | $30,000 | $35,000 | $40,000 | $45,000 | $50,000 |
| $1,500,000 | $45,000 | $52,500 | $60,000 | $67,500 | $75,000 |
| $2,000,000 | $60,000 | $70,000 | $80,000 | $90,000 | $100,000 |
| $3,000,000 | $90,000 | $105,000 | $120,000 | $135,000 | $150,000 |
Bottom Line
There is no single “safe” withdrawal rate for every retiree in 2026 — credible research spans roughly 3.7% (Morningstar’s conservative forward-looking estimate) to 4.7%+ (Bengen’s updated historical worst-case with a diversified portfolio). For a standard 30-year retirement with moderate stock allocation and no flexibility, treat 3.9-4.0% as a reasonable starting point. With dynamic spending rules (guardrails), guaranteed income covering essential expenses, and willingness to adjust spending by 5-10% in down years, the higher end of the range becomes more defensible. No fixed rule works in all conditions — building a flexible plan with a guaranteed floor is more important than finding the perfect percentage.
For more on FIRE strategies and numbers, see the FIRE hub.
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