Coast FIRE Calculator
Calculate your Coast FIRE number and find out exactly when you can stop worrying about retirement contributions.
What if you could stop contributing to your retirement accounts today never invest another dime and still wake up at 65 with a fully-funded retirement? Not a pipe dream. It's called Coast FIRE, and the math behind it is surprisingly straightforward.
Hit one specific number early enough, and compound interest becomes your full-time retirement manager. The Coast FIRE Calculator above tells you that exact number. Plug in your details and find out just how close you already are.
Table of Contents
What is Coast FIRE?
Coast FIRE is a milestone within the broader Financial Independence, Retire Early (FIRE) movement. The concept is elegantly simple: you invest enough money early enough that compound interest alone with zero additional contributions from you will grow that lump sum to your full retirement target by traditional retirement age.
Once you hit your Coast FIRE number, you don't need to retire immediately. You just need to cover your current living expenses. Your retirement is already fully funded in the background, quietly compounding while you live your life.
Think of it like rolling a snowball down a hill. Getting it started takes real effort that's the push. But once it's big enough and gravity takes over, you can stop pushing entirely. Coast FIRE is the moment gravity takes over.
Coast FIRE vs. Other FIRE Movements
The FIRE world has branched into several distinct flavors. Here's how they compare:
| FIRE Type | Definition | Best For |
|---|---|---|
| Coast FIRE | Invest a lump sum early; let compound interest grow it to your full retirement number without additional contributions. | People in their 20s–40s who want to reduce financial pressure without fully retiring yet. |
| Lean FIRE | Fully retire early on a lean budget (typically under $40,000/year). Requires aggressive saving and a frugal lifestyle. | Minimalists comfortable with tight budgets and intentionally low spending. |
| Fat FIRE | Fully retire early with a large portfolio supporting a comfortable or luxurious lifestyle ($100,000+/year in spending). | High earners who refuse to sacrifice their current lifestyle in early retirement. |
| Barista FIRE | Partially retire. Work part-time—often for health benefits—while your portfolio continues growing. | People escaping high-stress careers who aren't ready to stop working completely. |
Coast FIRE vs. Barista FIRE, what's the real difference? They're cousins. Both involve continuing to work after hitting a financial milestone. But Barista FIRE often means you're still relying on some portfolio growth or drawdown to make ends meet, while Coast FIRE means your retirement is genuinely on autopilot. You work purely to fund today, not tomorrow.
How to Use the Coast FIRE Calculator
The calculator is built to give you a precise, actionable number, not a ballpark. Here's what each input actually means and why it matters.
How They Determine Your Target FIRE Number
Your Target FIRE Number is the total portfolio value you need to fully retire. The calculator derives it with one clean formula: divide your desired annual spending by your Safe Withdrawal Rate.
If you plan to spend $60,000 per year in retirement and use a 4% SWR, your target is $1,500,000. The SWR answers a single question: "How big does my portfolio need to be so that withdrawing a fixed percentage each year covers my expenses, ideally forever?"
The most widely cited SWR is 4%, derived from the landmark Trinity Study, which examined 30-year retirement horizons across historical market cycles. If you're planning for a longer retirement, say, 40 to 50 years, many Certified Financial Planners recommend using a more conservative 3% to 3.5% to give yourself a meaningful safety margin.
Why You Must Use an Inflation-Adjusted Number
The US stock market has delivered roughly 10% in average annual nominal returns. But inflation has historically eroded around 2–3% of that. Your real, inflation-adjusted return lands closer to 7%.
This distinction matters enormously over 30–40 years of compounding. The calculator displays everything in today's dollars, so using a real return (rather than a nominal one) keeps your Coast FIRE number directly comparable to what things cost right now, no mental gymnastics required. 7% is a solid default for a broadly diversified equity portfolio.
The Magic Behind Your Coast FIRE Number
Your Coast FIRE number is calculated by working backwards from your Target FIRE Number. We know how large the portfolio needs to be at retirement, so we discount it back to today using your expected real return. The formula is:
Coast FIRE Number = Target FIRE Number ÷ (1 + r)^n
Where r = your real annual return rate, and n = years until retirement.
Every additional year between now and retirement makes that divisor larger, which makes your required Coast FIRE number smaller. Time is the entire game here.
This is why your starting age matters so dramatically. Consider someone targeting a $1,500,000 retirement portfolio with a 7% real return:
- Starting at age 25 (40 years of compounding): Coast FIRE number ≈ $147,000
- Starting at age 35 (30 years of compounding): Coast FIRE number ≈ $289,000
- Starting at age 45 (20 years of compounding): Coast FIRE number ≈ $568,000
The 25-year-old needs less than one-quarter of what the 45-year-old needs to hit the exact same retirement target. That's the raw, compounding power of starting early.
This also explains why Coast FIRE is such a psychologically powerful concept. Many people in their late 20s or early 30s are far closer to a form of financial independence than they realize. They just haven't run the numbers yet.
Frequently Asked Questions
What is a good Safe Withdrawal Rate (SWR)?
The most widely accepted SWR is 4%, based on the Trinity Study's analysis of 30-year retirement windows. For early retirees planning for 40–50 years, a more conservative 3% to 3.5% is commonly recommended by financial planners. The calculator defaults to 4%, but you should lower it if you expect a longer retirement or want extra buffer against sequence-of-returns risk.
Does the Coast FIRE Calculator account for inflation?
Yes, through the "Expected Real Annual Return" input. By entering your inflation-adjusted return (7% rather than the nominal 10%), all results are automatically expressed in today's dollars. Your Coast FIRE number and Target FIRE Number are directly comparable to what things cost right now, with no additional adjustment needed.
What happens after I hit my Coast FIRE number?
You can, in theory, stop contributing to retirement accounts entirely. Your only financial job becomes covering your current living expenses, which dramatically expands your career options. Many people use Coast FIRE as a launchpad: they switch to lower-stress or part-time work, start a business, or pursue something they actually love. The one non-negotiable rule: don't touch the retirement accounts. Let them compound undisturbed until you're ready to retire.
Is 7% a realistic real annual return to expect?
For a broadly diversified, equity-heavy portfolio (like a low-cost global index fund), 7% real return is a widely used, evidence-based baseline among financial planners. The S&P 500 has historically delivered roughly 10% nominal; subtracting ~3% for inflation gets you to approximately 7% real. Future returns are never guaranteed, but 7% is a reasonable planning assumption. More conservative investors often use 5–6% to build in an extra margin of safety.
Your Coast FIRE Number Is Waiting
Stop guessing. Stop assuming retirement is some distant, abstract thing you'll deal with later. Scroll up, plug in your numbers, and find out exactly when you can stop saving forever, and start coasting.
The math doesn't lie. And it might surprise you with how close you already are.