The honest answer to how long will my retirement savings last is that it depends on four moving parts: your withdrawal rate, your spending, your returns, and your lifespan. The most quoted rule of thumb — the 4% rule — traces back to research by financial adviser William Bengen, who tested withdrawal rates against decades of historical U.S. market data.
It was never a guarantee, only a starting point.
Most people never run the numbers at all. They guess, then adjust in a panic after a bad market year. That guesswork is expensive, because a withdrawal rate that is half a percentage point too high can shorten a portfolio's life by years.
This guide covers five practical checks that turn "it depends" into an actual range. You will learn how withdrawal rates, health care costs, market timing, and longevity change the answer — and which free tools will run the simulation for you.
1. Use the 4% Rule as a Starting Point, Not a Promise
The 4% rule says you withdraw 4% of your portfolio in year one, adjust that dollar amount for inflation each year, and have a strong chance of not running out over 30 years.
Bengen's 1994 research, later reinforced by the Trinity Study, found that a 4% initial withdrawal rate survived most historical 30-year periods using a balanced stock-and-bond portfolio. Note the emphasis: most, not all. That distinction is the whole answer to how long will my retirement savings last.
Your personal timeline shifts with three variables:
- Time horizon — 20 years is a different math problem than 40.
- Asset mix — too conservative and inflation erodes you; too aggressive and an early crash hurts.
- Flexibility — the ability to cut spending in bad years matters more than any single rate.
Why 30 Years Isn't a Magic Number
Retire at 60 and you may need 35 years of income. Retire at 70 and 20 is plausible. The 4% rule was built around the middle of that range, which is why it fits almost nobody perfectly.
The rule is a useful anchor for how long will my retirement savings last, but it is not personalized. It ignores your pension, your Social Security claiming age, and your actual spending pattern.
How to apply this: Multiply your portfolio by 0.04 to get a rough first-year income figure. Compare that number with your real annual spending — the gap tells you whether the plan is realistic before you touch a calculator.
2. Do the Math With Your Real Withdrawal Rate
Small changes in withdrawal rate have outsized effects on how long will my retirement savings last, because you are changing both the amount you remove and the balance left to compound.
Consider a $600,000 portfolio. At 4% you withdraw $24,000 in year one. At 5% you take $30,000 — a quarter more income, but a noticeably faster drawdown.
| Withdrawal rate | Income from $600,000 | Horizon it can suit | Action to take |
|---|---|---|---|
| 3.0% | $18,000 | 35+ years, early retiree | Save more or plan part-time work |
| 3.5% | $21,000 | 30-35 years | Test in a Monte Carlo calculator |
| 4.0% | $24,000 | About 30 years, balanced mix | Treat as a baseline only |
| 4.5% | $27,000 | 20-25 years | Keep a spending-cut plan ready |
| 5.0% | $30,000 | Under 20 years, or with a pension | Recheck every year |
Inflation Is the Quiet Variable
At 3% inflation, your $24,000 withdrawal must grow to roughly $32,000 by year 10 just to buy what it buys today. Skip that adjustment and your plan looks far healthier than it is.
Returns Matter Less Than You Think
Average returns get the headlines, but it is the real return — after inflation and fees — that determines how long will my retirement savings last. A 7% return with 3% inflation and 1% in fees is really about 3%.
How to apply this: Pick one withdrawal rate from the table and run it with inflation turned on. If the plan only survives when you ignore rising costs, you are not finished planning.
3. Cut the Costs That Drain Savings Fastest
Fees, taxes, and health care are the three leaks that most often shorten how long will my retirement savings last. None of them appears in a simple "portfolio divided by annual spending" estimate.
Investment fees compound against you. A fund charging 1% a year instead of 0.05% hands a meaningful slice of your long-term growth to the manager. Over 30 years, that difference is measured in years of retirement income, not basis points.
Health care is the largest wildcard. Fidelity's Retiree Health Care Cost Estimate has repeatedly put lifetime health care spending for a 65-year-old couple in the hundreds of thousands of dollars — and that figure excludes most long-term care.
Required Minimum Distributions Change Your Tax Bill
The IRS states plainly that "you can't keep retirement funds in your account indefinitely." Required minimum distributions generally begin at age 73 for people born between 1951 and 1959, and at 75 for those born in 1960 or later, according to the IRS required minimum distributions page.
That matters because forced withdrawals can push you into a higher tax bracket and raise your Medicare premiums. Taxes are part of how long will my retirement savings last, even though they never show up on a brokerage statement.
How to apply this: Open your account today and check the expense ratio on every fund you own. Anything above 0.20% needs a written justification — and if you cannot write one, move to a low-cost index fund.
4. Account for Longevity and Bad Market Timing
Longevity is the input most people underestimate. The Social Security Administration's period life table shows that someone who reaches age 65 can expect to live into their early-to-mid 80s on average — and averages conceal the fact that roughly half of people live longer than that.
For couples, the math gets harsher. The odds that at least one spouse reaches 90 are meaningfully higher than either person's individual odds, which means a household portfolio may need to fund a 30-year retirement even when each partner expects fewer years.
Understanding your life expectancy directly changes the answer to how long will my retirement savings last under realistic assumptions.
A bad sequence of returns early in retirement can dramatically shorten how long will my retirement savings last, even with conservative withdrawal rates.
