The 4% Rule Explained -And Why I Think There's a Better Way to Think About It

If you've spent any time in personal finance circles -Reddit, podcasts, YouTube -you've heard the 4% rule. It's the single most cited number in retirement planning. And for good reason: it's simple, it's memorable, and it's grounded in real research.

But I've come to think it's also a little misleading. Not wrong exactly -just incomplete in a way that sends people chasing a number that may not mean what they think it means.

Let me explain the rule, where it comes from, and then tell you why I prefer thinking about retirement differently.

What is the 4% rule?

The 4% rule comes from a 1994 paper by financial advisor William Bengen, later popularized as the "Trinity Study." The idea is simple: if you withdraw 4% of your portfolio in the first year of retirement -and adjust that amount for inflation each subsequent year -your money has historically lasted at least 30 years across every market period studied, including the Great Depression.

From that, you get a handy formula for your "FI number" (Financial Independence number): multiply your annual expenses by 25.

If you spend $5,000 a month, that's $60,000 a year. Your FI number is $1,500,000.

Simple enough. So what's my problem with it?

Where the 4% rule gets slippery

A few things bother me about using this as your primary planning metric.

It assumes you're selling assets. The 4% rule works by withdrawing from your principal -selling pieces of your portfolio each year to fund your life. That means your portfolio is designed to shrink over time, hitting zero around year 30 if the math works out. That feels uncomfortable to me. What if you live longer than 30 years? What if markets underperform in your early retirement years?

It ignores the income your portfolio generates. A $1.5M portfolio invested in diversified index funds at a 7% annual return generates roughly $105,000 per year in returns. You're spending $60,000. Your portfolio isn't just surviving -it's growing. But the 4% rule treats your portfolio like a countdown timer rather than an income-generating machine.

Your expenses aren't fixed. The rule adjusts withdrawals for inflation, but life doesn't work that cleanly. You'll have years with big medical bills, roof replacements, or a kid's tuition. And you'll have years where the mortgage is paid off and expenses drop dramatically. A single number can't capture any of that.

Most people have other income sources. The 4% rule calculation ignores Social Security, pensions, rental income, or part-time work. If you're planning to get $2,000/month from Social Security eventually, your portfolio doesn't need to cover 100% of your expenses -but the 25× formula has no way to account for that.

None of this makes the 4% rule wrong. It's a useful anchor. But treating it as the finish line creates a weird situation: you're chasing a single portfolio balance, while ignoring the actual question -can your money generate enough income to cover your life without you having to sell it?

The way I think about it instead: passive income vs. expenses

When I was trying to figure out if I could afford to retire early from the federal government, the 4% rule didn't give me the answer I needed. I needed to see, month by month, what my actual cash flow would look like -income from my pension, income from our portfolio, our expenses, and whether those numbers actually worked together.

What I really wanted to know was: when does my money start generating more than I spend?

That's a different question than "when does my portfolio hit X?" It's asking about the income your portfolio produces, not just its balance. And once your passive income -portfolio returns, dividends, pension, Social Security -covers your expenses, you're not depleting anything. You're living on yield. Your principal keeps growing.

That's what I call the Sweet Spot 🍯 -the first month where your passive income equals or exceeds your monthly expenses. It's a more intuitive milestone, and in my experience, a more motivating one. Instead of watching a portfolio balance creep toward an abstract number, you watch your passive income grow as a percentage of your expenses -40%, 60%, 80% -until it crosses 100%.

How these two approaches compare

They're not opposites. For a lot of people at typical retirement ages, the 4% rule and the passive income crossover happen at similar portfolio sizes. But there are cases where they diverge:

• Early retirees need a longer horizon than 30 years -the 4% rule gets conservative at 3–3.5%, which pushes your FI number up to 30–33× expenses. The passive income view actually gets easier at lower portfolio growth rates since you're not depending on selling assets.
• People with partial income sources (pensions, Social Security, rental income) can hit their passive income crossover much earlier than their 25× FI number because those income streams directly offset expenses.
• Variable spenders benefit from seeing cash flow month by month rather than just a lump sum target -because a year with no mortgage payment looks very different from a year with tuition.

How to figure out your actual number

The 4% rule gives you a rough target. But to know if you're actually ready, you need to model your specific situation -your income, your expenses, your growth rate, your timeline.

That's exactly what HoneyPlan does. You put in your actual income sources and expenses, pick a portfolio growth rate, and the projection grid shows you month by month what your cash flow looks like for the next 20–30 years -including when your passive income crosses your expenses.

You can toggle individual expenses on and off (what if the mortgage is paid off by then?), adjust your starting balance, and run multiple scenarios. The 4% rule gives you a starting benchmark. HoneyPlan shows you whether your specific life actually supports it.

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