What Is CoastFIRE? A Complete Beginner's Guide

If you've ever felt overwhelmed by retirement math — the idea that you need to save aggressively for 40 straight years — CoastFIRE is the concept that changes the game. It's the moment when you've saved enough that, even if you never contributed another dollar, compound growth alone would carry you to a full retirement.

In other words: once you hit your CoastFIRE number, you can stop saving. You still need to cover your living expenses, but you no longer need to fund your future retirement. Your existing portfolio does that job.

How CoastFIRE Works: The Core Idea

Traditional retirement advice says "save 15% of your income forever." CoastFIRE flips that by front-loading the savings. Put enough into investments early, and compound interest does the heavy lifting.

The CoastFIRE Formula

To calculate your CoastFIRE number, you need three inputs:

• Your target retirement number (typically 25× annual expenses, based on the 4% Safe Withdrawal Rate)
• Years until retirement
• Expected real return (nominal return minus inflation, usually ~5%)

The formula: CoastFIRE = FIRE Number ÷ (1 + r)^n

Where r is your real return and n is years until retirement. For example, if you need $1.5M at age 65 and you're 35 now with a 5% real return, your CoastFIRE number is roughly $347,000 today.

Who Is CoastFIRE For?

CoastFIRE tends to appeal most to:

• High-income professionals in their 20s and 30s who can front-load savings aggressively
• Burned-out workers who want the option to downshift without torpedoing retirement
• Parents looking to reduce hours or take a lower-paying role once kids arrive
• Career-changers who want to move into passion work without financial pressure

CoastFIRE vs Full FIRE

Full FIRE means saving enough to never work again. CoastFIRE is more flexible: you still work to cover living expenses, but you've freed yourself from the pressure to save. Many CoastFIRE-ers keep full-time jobs and simply redirect old savings into lifestyle upgrades — travel, better food, more time with family.

What Could Go Wrong?

CoastFIRE math assumes average returns. But markets aren't guaranteed. A bad decade early on — like the 2000s — can put you behind schedule. That's why it's worth running a Monte Carlo simulation to see the range of possible outcomes, not just the average case.

The Bottom Line

CoastFIRE isn't about quitting your job. It's about buying back optionality. Once you hit the number, work becomes a choice rather than a necessity — and that's the most underrated form of wealth there is.

Ready to see where you stand? Use the CoastFIRE Calculator to run your numbers with your actual income, expenses, and timeline.