Imagine working a job you genuinely like, not because you need to save for retirement, but simply to cover today's bills. That's the promise of Coast FIRE, a financial independence approach that has gained traction in the personal finance community over the past several years. Unlike traditional FIRE, which demands aggressive saving through your 30s and 40s to retire early completely, Coast FIRE sets a lower bar: you invest enough early in life so that, by the time you reach traditional retirement age, your investments will have grown to a standard nest egg without any additional contributions. The rest of your career then becomes optional—you can downshift to a lower-paying, more fulfilling job, work part-time, or simply save less. This article will walk you through the exact math behind Coast FIRE, how to calculate your personal Coast number, the real-world trade-offs you need to consider, and common mistakes that can derail your plan.
Coast FIRE is built on a single mathematical concept: compound growth. The core idea is that you accumulate a certain amount of money early in your career, stop contributing to retirement accounts entirely, and let that principal grow for 20, 30, or 40 years until it reaches a sum sufficient to support your desired retirement spending. At that point, your conventional retirement savings are fully funded; you only need to work to cover your current living expenses. For example, a 30-year-old who wants to retire at 60 with an annual spending of $40,000 (in today's dollars) and a 4% withdrawal rate needs a final nest egg of $1,000,000. Assuming an average 7% real return, they would need to have about $130,000 invested today — that's their Coast number. From 30 to 60, they contribute nothing more to retirement accounts and focus on earning enough for today's lifestyle. The key distinction from traditional FIRE: you don't retire early, you just stop saving for retirement. Your working years become about covering current costs, not future ones.
Start with your current expenses and adjust for retirement. Don't use the generic “70% of income” rule—it's too vague. Instead, track your actual spending for three months using a tool like Mint or YNAB (You Need A Budget). Then subtract costs that will vanish in retirement: mortgage payments (if you plan to own a home outright), commuting costs, and work wardrobe. Add in health insurance premiums you'll pay without employer subsidies, and a buffer for hobbies or travel. A realistic range for most people in the U.S. is $35,000 to $60,000 per household per year in today's dollars.
Multiply your annual retirement spending by 25. This is the standard 4% rule from the trinity study, which assumes a portfolio of 60% stocks and 40% bonds will last at least 30 years. For a $45,000 annual spend, that gives a target of $1,125,000. If you expect Social Security, you can reduce this target—for example, if you anticipate $18,000 per year from Social Security at full retirement age (67), your portfolio only needs to cover the remaining $27,000, for a $675,000 nest egg.
The Coast number is your target nest egg divided by (1 + annual real return)^years until retirement. Use a real return (accounting for inflation) of 5% to 7%—be honest with yourself. If you're 35, planning to retire at 65, targeting $1,000,000, and assuming 6% real return: $1,000,000 / (1.06)^30 = $174,000. That's how much you need invested today. Repeat for your numbers. Free online Coast FIRE calculators (like the one on WalletBurst) can do this instantly, but always double-check with your own formula.
Assume $2,000 monthly expenses in retirement (that's $24,000/year). Target nest egg: $600,000. A 25-year-old earner who can invest $50,000 by age 30 (very difficult on this income) would need 60% stocks/40% bonds growing at 6% to reach $600,000 by 65. More realistically, they might aim for a Coast number of $25,000 to $30,000 invested by 30, then plan to rely more heavily on Social Security—around $1,200/month for low earners. The catch: low earners often have little discretionary income to save aggressively early, making Coast FIRE harder to achieve without a windfall like an inheritance.
Target annual spending in retirement: $40,000. Nest egg goal: $1,000,000. If you start at 25 and want to Coast by 30, you need around $130,000 invested by age 30 (saving $21,667 per year for 5 years—a 31% savings rate). If you start later, say at 35, you'd need $230,000 invested by 40 to Coast to 65. That's about $38,000 per year for 5 years, a 54% savings rate. The window is tight; missing contributions in your early 30s drastically increases the Coast number.
Target spending: $60,000 annual in retirement. Nest egg: $1,500,000. A 25-year-old needs $200,000 invested by 30—achievable by saving $33,333 per year (22% of gross income). Or they could save $50,000 per year for 3 years and Coast by 28. High earners have the most flexibility, but they often err by spending too much on lifestyle inflation, pushing Coast numbers out of reach.
Many people assume they'll be healthy or that subsidies will cover them. But even with the Affordable Care Act, a couple aged 55 to 64 can pay $15,000–$25,000 per year in premiums and out-of-pocket costs for a silver plan. If you Coast at 40 and plan to work until 65 to cover expenses, you still need to pay for health insurance for 20+ years before Medicare kicks in. Build this into your annual spending estimate—don't ignore it.
The decade after you stop contributing is the most dangerous. A 2008-style crash hitting a $200,000 portfolio could drop it to $120,000. Even with 10 years of recovery, if the crash happens in year 1 of Coasting, you end up with far less than expected. Mitigate this by keeping 10%–20% of your Coast portfolio in bonds or cash during the first 5–10 years, then shifting to stocks once the portfolio is larger. Yes, this lowers expected returns, but it protects against catastrophic drawdowns.
Coast FIRE requires you to earn enough to live on from age X until traditional retirement. If you switch to a low-paying dream job that barely covers rent, but then lose that job at 55, you may struggle to find another that pays any living wage. Always have a backup plan: maintain skills that are in demand, keep a small emergency fund separate from your Coast portfolio (6–12 months of expenses), and consider keeping a small part-time gig that you can scale up if needed.
Requires saving 50%+ of income for 10–15 years. Gives you full independence (no work required). Coast FIRE requires less up-front saving but forces you to keep some form of employment for decades. Traditional FIRE is for those who hate their jobs; Coast FIRE is for those who like their jobs but want to remove financial pressure.
Barista FIRE is Coast FIRE plus a small part-time job that covers a portion of expenses—typically with health insurance benefits. Barista FIRE assumes your portfolio covers 50%–70% of expenses, while work covers the rest. Coast FIRE assumes work covers 100% of current expenses, and the portfolio handles future retirement. Both require similar savings rates early on; the difference is in how much you depend on employment income.
Lean FIRE is about minimizing expenses, not about the Coasting period. You can combine Lean FIRE with Coast—aim for a $25,000 annual spend and you'll need a smaller Coast number. But cutting expenses too low can make you vulnerable to inflation or unexpected costs. Coast FIRE works best when you have a realistic, not aspirational, spending target.
The appeal of Coast FIRE isn't an early retirement in the traditional sense—it's the freedom to reshape your working life on your own terms. By front-loading your retirement savings and then letting compound growth carry the rest, you can afford to choose work that you find meaningful, even if it doesn't pay as well. But the strategy only works if you run the numbers honestly, prepare for market turbulence, and stay disciplined about not touching the Coast portfolio. Start with a single step: calculate your current expense baseline and your Coast number this week. The sooner you know where you stand, the sooner you can decide whether this path aligns with the life you actually want to live.
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