Have you ever wondered when you can stop saving for retirement and let your existing investments do the work? The coast FIRE calculator answers that question. Coast FIRE - sometimes called coast FI - is the point at which your current portfolio, left untouched, will grow through compound interest to reach your full retirement number by a target age. Once you reach your coast FIRE number, you no longer need to save. You only need to earn enough to cover today’s living expenses.
This coast FIRE calculator determines exactly how much you need invested right now so that compound growth carries you to financial independence. Whether you are 25 and just starting to wonder “can I coast to retirement?” or 40 and evaluating whether your portfolio is large enough, this coast FI calculator gives you a clear, data-driven answer.
How the Coast FIRE Calculator Works
The coast FIRE calculator uses a straightforward present value formula. It takes your desired retirement spending, applies the 4% rule (from the Trinity Study) to determine your full FIRE number, then discounts that amount back to today using your expected real rate of return and the number of years until your target retirement age. The result is your coast FIRE number - the portfolio value you need right now.
For example, if you want to spend $48,000 per year in retirement, your full FIRE number is $1,200,000 (using the 25x rule). If you are 30 years old, plan to retire at 60, and expect a 7% nominal return (roughly 4% real after inflation), your coast FIRE number is approximately $370,000. If your portfolio already exceeds $370,000, you have reached coast FIRE and can stop saving for retirement entirely.
Calculate Your Coast FIRE Number
Enter your current age, target retirement age, current portfolio value, expected rate of return, and planned annual retirement spending. The calculator shows your coast FIRE number, whether you have already reached it, and how your portfolio is projected to grow over time through compound interest alone.
Understanding the Coast FIRE Number and Compound Interest
The coast FIRE number relies entirely on the power of compound interest - the principle that investment returns generate their own returns over time. Historical data from the S&P 500 shows an average annual return of approximately 10% nominal (7% after inflation) over rolling 30-year periods. This means money invested in a diversified index fund has historically doubled roughly every 10 years in real terms.
This is why the coast FIRE number drops dramatically the younger you start. A 25-year-old targeting retirement at 60 has 35 years of compound growth ahead. Their coast FIRE number might be just $250,000. A 40-year-old with only 20 years until retirement needs closer to $550,000 - more than double - because there is less time for compounding to work. The coast FIRE calculator above shows exactly how age and timeline affect your number.
When Can I Stop Saving for Retirement?
This is the central question behind coast FIRE, and the answer depends on three variables: how much you have saved, what return you expect, and when you plan to retire. Many people who have been diligent savers in their 20s and early 30s discover they can stop saving for retirement far sooner than they assumed. The psychological relief is significant - shifting from “I must save $2,000 per month or I will never retire” to “I have already saved enough; I just need to cover my current expenses” changes how you think about career choices, risk, and daily life.
If you are asking “can I coast to retirement?” but your portfolio is not quite large enough, the calculator also shows how much more you need. Often, the gap is smaller than expected - a few more years of aggressive saving, or a modest reduction in your target retirement spending, can close it entirely.
Coast FIRE and Geographic Arbitrage
Coast FIRE pairs naturally with geographic arbitrage. Once you reach your coast FIRE number, you only need to earn enough for current living expenses - not save for retirement on top of that. In a low-cost country, covering expenses might require only $1,000 to $1,500 per month, achievable through part-time remote work, freelancing, or teaching English abroad.
Use the Geographic Arbitrage FIRE Calculator to compare living costs across destinations. Moving abroad also lowers your eventual FIRE number (since you will spend less in retirement), which in turn lowers your coast FIRE number today. The Retirement Visa Eligibility Checker shows which countries will grant residency based on your income level.
Coast FIRE vs. Barista FIRE vs. Lean FIRE
These three FIRE variants each address the question of when you can stop saving for retirement, but from different angles. Coast FIRE says “stop saving and let compound interest finish the job.” Barista FIRE says “work part-time and use that income plus portfolio withdrawals to cover expenses.” Lean FIRE says “reduce your spending to essentials so you need a smaller portfolio.”
You can combine these approaches. Someone who has reached their coast FIRE number might also work part-time (barista FIRE) to avoid drawing down the portfolio at all, allowing it to grow even faster. Or they might adopt a lean FIRE budget abroad, lowering both current expenses and their eventual retirement target. The Expat Tax Burden Estimator helps you understand the tax implications of each scenario, and the FEIE Pre-Screener shows which income qualifies for the Foreign Earned Income Exclusion.
Risks and Limitations of the Coast FIRE Strategy
Coast FIRE depends on long-term market returns matching historical averages. If you experience a prolonged bear market or lower-than-expected returns in the early years after you stop saving, your portfolio may not reach your target by retirement age. The Trinity Study provides strong evidence for the 4% rule over 30-year periods, but individual outcomes vary. Sequence-of-returns risk - the danger of poor returns early in a long time horizon - can derail even well-planned projections.
To mitigate this, many coast FIRE practitioners maintain flexibility. They continue saving small amounts when income allows, pick up freelance work during market downturns, or adjust their target retirement age by a few years. The coast FI calculator above assumes a constant rate of return; in reality, returns are volatile, and maintaining some financial flexibility is prudent.
Another consideration is inflation. The coast FIRE calculator uses real returns (after inflation), but unexpected spikes in inflation can erode purchasing power faster than projected. Retirees who plan to live abroad may face additional currency risk if their portfolio is denominated in US dollars but their expenses are in a local currency. Check the Social Security Abroad Checker if you plan to supplement your retirement portfolio with Social Security benefits while living overseas - having multiple income streams reduces your dependence on portfolio performance alone.
Frequently Asked Questions About Coast FIRE
What is a good coast FIRE number?
Your coast FIRE number depends on your age, target retirement age, expected returns, and desired retirement spending. For a 30-year-old planning to retire at 60 with $40,000 per year in spending, a typical coast FIRE number falls between $300,000 and $400,000 assuming a 4% real return. Use the coast FIRE calculator above to find your specific number.
Can I coast to retirement at 35?
Yes, but your coast FIRE number will be higher because you have fewer years for compound interest to work. At 35 targeting retirement at 60, you need roughly 50% more than a 25-year-old with the same retirement target. The coast FI calculator shows how age affects the math and whether your current savings are sufficient.
When can I stop saving for retirement?
You can stop saving for retirement once your invested portfolio equals or exceeds your coast FIRE number. At that point, compound interest on your existing investments, based on historical S&P 500 returns, is projected to grow your portfolio to your full FIRE number by your target retirement age without any additional contributions.
What is the difference between coast FIRE and coast FI?
Coast FIRE and coast FI refer to the same concept. “FI” stands for financial independence, and “FIRE” adds “retire early.” Both describe the milestone at which your existing investments will grow to support full retirement without further savings. The terms are used interchangeably in the financial independence community.
Is coast FIRE realistic?
Coast FIRE is mathematically sound based on historical stock market data. The S&P 500 has delivered average annual returns of approximately 10% nominal over long periods. The main risk is that future returns may differ from past performance. Building flexibility into your plan - such as the ability to save modestly or work part-time if needed - makes the strategy more robust.
How does coast FIRE work with retiring abroad?
Coast FIRE and retiring abroad complement each other well. Living in a lower-cost country reduces your current expenses (so you need less earned income while coasting) and reduces your retirement spending target (which lowers your coast FIRE number). Use the Geographic Arbitrage FIRE Calculator and UK Frozen Pension Loss Calculator to model specific international scenarios.
Coasting abroad? Wise moves your part-time income or drawdown at the mid-market rate with a $5-15 fee.