Disclaimer: This article is for educational purposes only and does not constitute financial or investment advice. Retirement planning involves many personal variables. Always consult a qualified financial advisor before making withdrawal decisions.
The Simple Formula: How to Calculate How Long Your Retirement Savings Will Last
Before we dive into complex strategies, here's the basic math that underlies every retirement calculator:
Years Savings Will Last = Current Savings ÷ (Annual Withdrawals − Annual Investment Returns)
But this oversimplifies reality. A more accurate approach uses amortization-style math that accounts for:
- Your starting balance
- Your monthly withdrawal amount
- Your expected annual rate of return
- The inflation rate
- Taxes on withdrawals
- Other income sources (Social Security, pension, rental income)
The Step-by-Step Calculation Method
Step 1: Calculate your annual income gap
Annual Income Gap = Total Annual Expenses − Guaranteed Annual Income (Social Security + Pension + Annuities)
Step 2: Estimate your withdrawal rate
Withdrawal Rate = Annual Income Gap ÷ Total Retirement Savings
Step 3: Stress-test against inflation
Real Return = Portfolio Return − Inflation Rate
If your portfolio earns 6% and inflation is 3%, your real return is 3%. If you withdraw more than 3% annually, you're eating into principal.
Step 4: Project year by year
Reduce your balance by withdrawals, grow the remainder by (return − inflation), and repeat until the balance hits zero. The number of years it takes = how long your savings last.
Worked Example: Will $1 Million Last 30 Years?
Let's walk through a realistic 2026 scenario for a 65-year-old retiree.
Retiree Profile:
- Starting retirement savings: $1,000,000
- Monthly expenses: $5,000 ($60,000/year)
- Social Security benefit: $2,000/month ($24,000/year)
- Pension: $0
- Portfolio allocation: 60% stocks / 40% bonds
- Expected annual return: 6%
- Inflation rate: 3%
- Tax rate on withdrawals: 12%
Step 1: Income Gap
$60,000 expenses − $24,000 Social Security = $36,000/year must come from savings
Step 2: Initial Withdrawal Rate
$36,000 ÷ $1,000,000 = 3.6%
Step 3: Real Return After Inflation
6% return − 3% inflation = 3% real return
| Year | Starting Balance | Withdrawal | Growth (6%) | Ending Balance |
|---|---|---|---|---|
| 1 | $1,000,000 | $36,000 | $57,840 | $1,021,840 |
| 10 | $1,215,000 | $46,900 | $72,090 | $1,240,190 |
| 20 | $1,380,000 | $63,100 | $79,020 | $1,395,920 |
| 30 | $1,180,000 | $84,800 | $65,710 | $1,160,910 |
Result: At a 3.6% initial withdrawal rate with 6% returns and 3% inflation, $1 million lasts indefinitely — the portfolio actually grows over 30 years.
The 4% Rule: What It Is, Why It Changed in 2026, and What to Use Instead
What Is the 4% Rule?
In 1994, financial planner William Bengen studied historical market data from 1926–1992 and discovered that retirees could safely withdraw 4% of their portfolio in year one, then increase that amount by inflation each year, without running out of money over a 30-year retirement.
Example: $1 million portfolio → $40,000 in year one. If inflation is 3%, withdraw $41,200 in year two, and so on.
What Changed in 2026?
Morningstar's 2026 "State of Retirement Income" report updated the safe withdrawal rate to 3.9% — up from 3.7% in 2025 but still below the traditional 4%.
Meanwhile, William Bengen himself — the creator of the 4% rule — now recommends 5.25% to 5.5% for diversified portfolios in his 2026 book, arguing the original rule was overly conservative.
| Source | 2026 Safe Withdrawal Rate | Assumptions |
|---|---|---|
| Morningstar | 3.9% | 30-year horizon, 90% confidence |
| William Bengen (original creator) | 5.25%–5.5% | Diversified portfolio, modern markets |
| Schwab (20-year horizon) | 5.3%–5.9% | Moderately conservative allocation |
| Vanguard | 3.5%–4.0% | Conservative projections |
The honest answer: There is no single "safe" rate. The right withdrawal rate depends on your age, portfolio mix, flexibility, guaranteed income, and risk tolerance.
7 Factors That Determine How Long Your Savings Last
1. Your Withdrawal Rate
This is the single biggest factor. A 1% difference in withdrawal rate can mean the difference between money lasting 25 years or 40 years.
2. Sequence of Returns Risk
Two retirees with identical average returns can have wildly different outcomes depending on when market crashes happen. A 30% drop in your first three years of retirement does permanent damage that later gains can't fully repair.
Protection strategy: Keep 2–3 years of expenses in cash or short-term bonds so you don't have to sell stocks during a crash.
3. Inflation
At 3% annual inflation, your purchasing power is cut in half in 23 years. At 4% inflation, it takes just 18 years. Your withdrawals must increase each year just to maintain the same standard of living.
4. Investment Returns
Vanguard and Schwab both project below-average returns for stocks and bonds over the next decade compared to historical norms. If your plan assumes 8% returns and you get 5%, your savings will deplete years earlier than projected.
5. Healthcare Costs
Fidelity estimates the average 65-year-old couple will need $315,000 for healthcare in retirement (2026 estimate). Medicare doesn't cover everything, and long-term care can cost $100,000+ per year.
6. Taxes on Withdrawals
Traditional 401(k) and IRA withdrawals are taxed as ordinary income. A retiree in the 22% bracket who withdraws $50,000 only keeps $39,000. Roth accounts are tax-free but require decades of prior planning.
7. Longevity
A 65-year-old man has a 20% chance of living to 90. A 65-year-old woman has a 30% chance. If you're married, there's a 50% chance one of you lives to 92. Planning for a 30-year retirement may not be long enough.
How to Make Your Savings Last Longer: 8 Proven Strategies
- Delay Social Security until age 70. Every year you delay past full retirement age increases your benefit by ~8%. A $2,000/month benefit at 67 becomes ~$2,480 at 70 — permanently.
- Use a dynamic withdrawal rate. Withdraw 5% in good years, cut to 3% in bad years. Flexibility adds years to your portfolio.
- Work part-time for 2–3 years. Even $20,000/year in part-time income reduces your withdrawal rate by 0.5–1%.
- Downsize your home. Moving from a $500,000 home to a $300,000 home frees up $200,000 in tax-free principal and reduces property taxes and maintenance.
- Consider a single-premium immediate annuity (SPIA). For a lump sum, an insurance company guarantees lifetime income. Not right for everyone, but useful for covering fixed expenses.
- Reduce investment fees. A 1% annual fee on a $1 million portfolio costs $10,000/year — equivalent to a 1% higher withdrawal rate. Use low-cost index funds.
- Plan for tax efficiency. Withdraw from taxable accounts first, then traditional IRAs, then Roth IRAs last. This minimizes taxes and lets tax-advantaged money grow longer.
- Review your plan annually. Market conditions change. Your health changes. Your spending changes. A plan set at age 65 will be wrong by age 75 if you never update it.