The Idea, Stripped Down

Early retirement isn't a lottery ticket. It's an arithmetic problem with three inputs: what you spend, what you save, and what your money earns. When those numbers cross a specific threshold, you can stop trading time for income. That threshold has a name — your FI number — and the path to it has a name too: financial independence, retire early, or FIRE.

The number itself comes from a simple inversion. If you withdraw 4% of your portfolio each year, your portfolio needs to be 25 times your annual spending. Spend $50,000 a year and you need $1.25 million. Spend $80,000 and the target is $2 million. The lesson here isn't the rule — you'll calculate it yourself in the next lesson. It's that two people earning the same income can have wildly different FI dates, because the math is anchored to spending, not earning.

The Four Flavors

You'll see four shorthand names in the FIRE community. They're useful because the underlying lifestyle assumption changes the math.

• Lean FIRE — annual spending of $25,000–$40,000. Portfolio: roughly $625K–$1M.
• Traditional FIRE — $40,000–$80,000. Portfolio: $1M–$2M.
• Fat FIRE — $100,000+. Portfolio: $2.5M+.
• Coast / Barista FIRE — a hybrid. You save aggressively enough that compounding alone gets you to traditional retirement age, but you keep working part-time (or in a lower-stress job) until then.

We don't pick a flavor in this course. That's a question of values, not math. But we do cover the practical decision framework for which variant fits which life at the end. For the deeper breakdown of who chooses what and why, our Early Retirement & FIRE explainer is the full reference.

Why Spending Matters More Than Income

A high-income earner who spends most of their salary is on a treadmill — they need a huge portfolio to fund a huge lifestyle. A modest earner who keeps lifestyle inflation in check is on a runway. The compounding lever is savings rate — the percentage of your take-home income you actually invest — and the relationship between savings rate and years-to-FI is staggeringly nonlinear. We unpack that math in The Savings Rate Lever.

For now, just sit with the implication: the most expensive thing about wanting to retire early is the lifestyle you commit to funding for the rest of your life. Every $1,000 of recurring annual expense adds $25,000 to your FI number at a 4% withdrawal rate.

Who This Course Is For

This course assumes:

• You have steady income and at least some capacity to save.
• You understand basic investing (if not, our Investing for Beginners course covers the foundation).
• You're U.S.-based — most of what follows references 401(k), Roth IRA, HSA, ACA, and Medicare, which are U.S.-specific systems.
• You want to make decisions about your specific situation, not just learn theory.

If "retire at 35" sounds unrealistic to you, that's fine. The same plan that gets a determined saver to FI by 35 also gets a more relaxed saver to FI at 55 — fifteen years before normal retirement age. The math doesn't care about labels.

What You'll Build in This Course

By the end you'll have:

• Your specific FI number, with sensitivity to spending and withdrawal rate.
• A savings rate target that puts you on the timeline you want.
• An account-funding waterfall that gets you the maximum tax leverage.
• A bridge plan to access your money before 59½ without penalties.
• A healthcare coverage plan from your last day of work until Medicare at 65.
• A withdrawal strategy that survives sequence-of-returns risk.

That's the entire problem. We'll do it one lesson at a time, with a hands-on FIRE calculator in Lesson 2 you can return to as your inputs change.