The 4% rule says you can withdraw 4% of your investment portfolio in your first year of retirement, adjust that amount for inflation each year after, and have a high chance of your money lasting 30 years. Flip it around and it becomes a target: you need roughly 25 times your annual expenses invested to retire. This guide explains where the number comes from, how to calculate yours, and where the rule breaks down — so you can use it without trusting it blindly. Monavio turns your real spending into a personal FIRE number and stress-tests it with Monte Carlo projections, so the math below stops being a guess.
What the 4% Rule Actually Says
The rule is simpler than most people think. Take your portfolio value on the day you retire. Multiply by 4%. That is your spending budget for year one. Every following year, you increase that dollar amount by inflation — not by 4% of the new balance.
Here is what that looks like with a $1,000,000 portfolio:
- Year 1: Withdraw 4% = $40,000
- Year 2 (3% inflation): Withdraw $40,000 + 3% = $41,200
- Year 3 (3% inflation): Withdraw $41,200 + 3% = $42,436
Notice the withdrawal grows with inflation regardless of what the market does. In a great year your balance climbs and the 4% becomes a smaller slice. In a bad year the dollar amount still rises, which is exactly when the rule gets stress-tested. That asymmetry is the whole game.
The Inverse: The 25x Rule
Because 4% is one twenty-fifth (1 ÷ 0.04 = 25), the rule doubles as a savings target. Multiply your annual expenses by 25 and you get the portfolio size that supports a 4% withdrawal.
Target Portfolio = Annual Expenses × 25
This is the foundation of the FIRE (Financial Independence, Retire Early) movement. If you want a deeper walkthrough of that target, see our guide on how to calculate your FI number. The two concepts are the same coin: the 4% rule tells you how much to withdraw; the 25x rule tells you how much to accumulate.
Where the 4% Rule Came From
The number is not arbitrary. It traces to two pieces of research from the 1990s.
- The Bengen study (1994). Financial planner William Bengen tested historical US market data going back to 1926. He looked for the highest withdrawal rate that would have survived every 30-year period, including retirees who started just before the 1929 crash or the 1970s stagflation. The answer was about 4%.
- The Trinity Study (1998). Three professors at Trinity University expanded the analysis across different stock/bond mixes and time horizons. They confirmed that a portfolio of roughly 50-75% stocks, withdrawing 4% adjusted for inflation, survived 30 years in the vast majority of historical cases.
Two things matter here. First, the studies are based on historical US returns — past performance, not a guarantee. Second, “high success rate” is not “100% guaranteed.” The 4% rule is a planning heuristic, not a law of physics.
How to Calculate Your Own Number
The rule is only as good as the expense figure you plug into it. Most people guess, and most guesses are low — sometimes by 20-30%. The fix is real data.
Step 1: Find Your True Annual Spending
Your FI number is built on expenses, not income. Someone earning $200,000 but spending $50,000 needs the same portfolio as someone earning $70,000 and spending $50,000.
To get an accurate figure, review at least 3-6 months of actual transactions. The fastest way is to upload your bank and card statements to Monavio and let AI categorization sort every transaction automatically — no manual tagging, no bank login required. You get a clear breakdown of where your money actually goes, which is the only honest input for this math.
Step 2: Adjust for Your Post-Retirement Life
Today’s spending is not tomorrow’s. Before you multiply, think through:
- Mortgage: Will it be paid off by your target date? That can cut housing costs dramatically.
- Healthcare: In countries without universal coverage, early retirees often buy their own insurance — frequently the single largest new line item.
- Commuting and work costs: Often disappear.
- Travel and hobbies: Often increase, sometimes a lot.
Step 3: Multiply by 25
Once you have a realistic annual figure, apply the formula. Here is a reference table:
| Annual Expenses | 4% Annual Withdrawal | Portfolio Needed (×25) |
|---|---|---|
| $20,000 | $20,000 | $500,000 |
| $30,000 | $30,000 | $750,000 |
| $40,000 | $40,000 | $1,000,000 |
| $50,000 | $50,000 | $1,250,000 |
| $60,000 | $60,000 | $1,500,000 |
| $80,000 | $80,000 | $2,000,000 |
| $100,000 | $100,000 | $2,500,000 |
The table reveals the core FIRE insight: cutting expenses works twice. Lowering spending from $60,000 to $50,000 shrinks your target by $250,000 and raises your savings rate, so you reach the smaller number faster.
The 4% Rule’s Biggest Weakness: Sequence-of-Returns Risk
The single most important caveat is timing. Two retirees can earn the exact same average return over 30 years and end up in wildly different places — one comfortable, one broke — purely because of when the bad years hit.
The danger zone is the first 5-10 years of retirement. If a major crash arrives early, you are selling shares at depressed prices to fund withdrawals, which permanently shrinks the base that needs to recover. This is called sequence-of-returns risk, and a single average return number completely hides it.
Why a Single Number Misleads You
Consider two retirees who both average 7% over their first decade:
- Retiree A gets +20%, +15%, +10% in the early years, then losses later. Their portfolio grew first, so withdrawals barely dented it.
- Retiree B gets -20%, -15%, -10% in the early years, then strong gains later. They drained capital while it was cheap, and the recovery had less to work with.
Same average. Very different outcomes. This is exactly why a flat “multiply by 25 and you’re done” calculation can give false confidence.
How to See the Real Risk: Monte Carlo
To account for timing, planners use Monte Carlo simulation — running thousands of randomized return sequences and reporting a probability of success rather than a single answer. Instead of “you have $1,000,000, you’re fine,” you get something like “this portfolio survives 40 years in 92% of simulated scenarios.”
Monavio’s FI planning feature runs Monte Carlo projections on your actual spending data and lets you pull what-if levers — change your savings rate, retirement age, or withdrawal rate and watch the success probability move. If you want to model the full timeline, our FIRE calculator walks through the inputs in detail. It turns a static rule of thumb into a stress test you can actually trust.
Is 4% Still the Right Number in 2026?
This is the live debate, and there is no single answer. Here is where the arguments land:
The Case for a Lower Rate (3% to 3.5%)
- The original studies assumed a 30-year horizon. Someone retiring at 40 needs the money to last 50+ years, and the 4% success rate drops as the horizon stretches.
- Some analysts argue that elevated valuations and lower expected bond yields mean future returns may trail the historical averages the rule was built on.
- A lower rate is simply a bigger safety buffer. Dropping from 4% to 3.5% means a 28.6x target instead of 25x — more to save, but more resilient.
The Case for Sticking with 4% (or Higher)
- The 4% rule already survived the worst historical sequences, including the Great Depression and 1970s stagflation. It was designed to be conservative.
- Real retirees are not robots. They naturally trim spending in down years, which dramatically improves portfolio survival versus the rigid model.
- In many historical periods, the retiree died with more money than they started with. The 4% rule frequently leaves a large surplus.
| Withdrawal Rate | Multiplier | Best Suited For |
|---|---|---|
| 3.0% | 33.3x | 50+ year horizons, maximum caution |
| 3.5% | 28.6x | Early retirees (40s), conservative |
| 4.0% | 25.0x | Traditional 30-year retirement |
| 4.5% | 22.2x | Shorter horizons, flexible spenders |
| 5.0% | 20.0x | Late retirees, large guaranteed income |
The practical middle ground most FIRE planners use: anchor on 4%, but build in flexibility — a willingness to cut discretionary spending 10-15% during a major downturn. That flexibility is worth more than any single percentage point.
Adjusting the Rule for Your Situation
The base formula is a starting point. A few common adjustments make it more accurate:
- Guaranteed income. If you expect a pension, Social Security, or rental income, subtract it from expenses before multiplying. If expenses are $50,000 and a pension covers $15,000, your portfolio only needs to fund $35,000 → a $875,000 target instead of $1,250,000. But if you retire before that income starts, you still need the full amount for the gap years.
- Taxes. Withdrawals from pre-tax accounts are taxable income in many jurisdictions. Build the tax cost into your expense figure, not as an afterthought.
- Inflation. You do not need to add a separate inflation line. The 4% rule already bakes in annual inflation adjustments — that is what the historical studies modeled.
- Geography. Costs vary enormously by country. If you plan to retire somewhere cheaper, base the math on that location’s expenses. Monavio handles any currency and any country’s bank statements, so multi-country tracking does not break your numbers.
Tracking Your Progress to the Number
Calculating the target is step one. The motivating part is watching the gap close. The metrics worth tracking monthly:
- FI percentage: invested assets ÷ target × 100
- Savings rate: the strongest predictor of how fast you arrive — see how to track your savings rate
- Net worth trajectory: is it climbing on pace?
- Projected FI date: based on current savings and assumed returns
A higher savings rate compresses the timeline far more than chasing extra return does. Going from a 20% to a 50% savings rate can cut decades off your path, because it lowers the target and accelerates contributions at the same time. If FIRE itself is new to you, start with what financial independence (FIRE) really means.
Start your free 14-day trial — no credit card required. Upload your statements, see your real spending, and watch Monavio turn it into a personal FIRE number with Monte Carlo projections. Plans start at $3/month; compare them on the pricing page.
Frequently Asked Questions
Is the 4% rule guaranteed to work?
No. It is a historical heuristic with a high success rate, not a guarantee. The original studies showed that 4% survived nearly every 30-year period in US market history, but “nearly every” is not “every,” and future returns could differ from the past. Treat it as a strong starting estimate, then stress-test it with a probability-based tool before relying on it.
How much do I need to retire on the 4% rule?
Multiply your expected annual expenses by 25. If you plan to spend $40,000 a year, you need roughly $1,000,000; at $60,000 a year, about $1,500,000. The key is using an accurate expense figure based on tracked spending, not a guess — underestimating expenses is the most common way people build a target that is too low.
Does the 4% rule include Social Security or a pension?
The base rule does not, but you can adjust for it. Subtract any guaranteed annual income from your expenses before multiplying by 25, since your portfolio only needs to cover the remainder. Just remember that if you retire before that income begins, you need the full amount to bridge the gap years.
Should I use 4% or a lower rate for very early retirement?
For a 50+ year horizon, many planners drop to 3.5% (a 28.6x target) or even 3% (33.3x) for extra safety, because longer timelines reduce the historical success rate of 4%. The trade-off is a larger portfolio. A reasonable compromise is to plan at 4% but stay flexible — being willing to cut spending in bad years often matters more than the exact starting rate.
What is sequence-of-returns risk?
It is the danger that a market crash early in retirement permanently damages your portfolio because you are withdrawing money while prices are low. Two retirees with identical average returns can have very different outcomes depending purely on the order those returns arrive. A single average return figure hides this risk entirely, which is why Monte Carlo simulations — running thousands of randomized return sequences — give a far more honest picture.
This article is for educational purposes only and does not constitute financial advice.