How to Calculate Coast FIRE Number: Free Coast FI Calculator

Calculate Coast FIRE number and discover exactly when your investments can grow on their own — freeing you from the pressure to keep saving for retirement. Imagine no longer needing to invest for the future because your portfolio is already compounding toward a fully funded retirement.

That’s the power of Coast FI, and our free Coast FIRE calculator shows you when you’ll get there — step by step. Let’s dive in and see how close you already are to your Coast FI goal.

💡 Before We Start – Try It Yourself – Coast FIRE Calculator

Want to know when you can stop saving for retirement and let your investments coast toward financial freedom? Run your numbers in our FREE Coast FIRE Calculator to see exactly when your portfolio can grow on its own—no new contributions needed.

👉 LAUNCH THE CALCULATOR and discover how close you already are to your Coast FI goal.

How to Calculate Coast FIRE Number

You can calculate Coast FIRE number with our free Coast FIRE Calculator at the end of this post. This number marks the point when you’ve invested enough in your retirement accounts so your portfolio can grow — without any further contributions — into a fully funded retirement by your target retirement age.

Your Coast FIRE number depends on your chosen withdrawal rate, which we cover in the next section.

Once you hit your Coast FIRE number, you can stop adding new money (as long as you’re not withdrawing yet) and let compound interest work in the background.

We’ve also created a free Compound Interest Calculator to make this process simple. While real market growth is never perfectly linear, history shows that over the long term, markets trend upward.

Here are some further resources to learn more about investment growth:

• The Simple Path to Wealth
• Decoding Market Growth: Key Drivers Behind The Market’s Upward Trend
• The Market’s Singular Direction: Upwards – A Historical Perspective

Understanding the Baseline – Your FIRE Number

Behind your Coast FI number lies your FIRE number — the total amount you need in your investment portfolio so the passive income it generates can cover your expenses indefinitely, without the risk of running out of money. This figure depends on how much you plan to withdraw each year, also known as your withdrawal rate (see below).

For example, let’s assume your expected annual retirement spending is 30.000. Using a safe withdrawal rate of 4% (see below), you would multiply 30.000 × 25 to get a FIRE number of 750.000. With this amount invested, withdrawing 4% annually could provide 30.000 per year for roughly 30 years — with a very high probability of never depleting your portfolio during that time.

So, when you calculate Coast FIRE number, be sure to review and recalculate your FIRE number whenever life changes — that way, you can adjust in time.

The Impact of Your Withdrawal Rate on Your Coast FI Number

The withdrawal rate is the percentage you can withdraw from your portfolio each year in retirement without running out of money. It depends on your retirement horizon — whether you’re planning for 20, 30, or 40+ years.

Your withdrawal rate has a direct influence on your Coast FI and FIRE number.

Many in the FIRE community use the 4% rule, which assumes you can withdraw 4% annually for about 30 years with a high probability of success. If your retirement is shorter (20–25 years), you might increase that to 5–6%. The older you are and the shorter your retirement, the higher the rate you can safely use.

If your retirement will last longer than 30 years — common for early retirees in their 40s or younger — consider lowering your rate to 3–3.5% for extra safety.

So, when you calculate Coast FIRE number, keep in mind that your withdrawal rate directly shapes your Coast FIRE target — even small changes can shift your entire timeline.

We’ve covered the proven Early Retirement Withdrawal Strategies on our blog so you can choose what’s right for your financial independence journey.

The Danger Of Not Taking Inflation Into Account

Our free Coast FIRE Calculator takes inflation into account. That’s because inflation is the process behind raised prices for any goods you want to purchase with your money. That is called your purchasing power. So, if you want your purchasing power to remain the same in retirement, you need to consider inflation.

Or in other words, you will need more money (than you need now) to buy the same things. So, if you want to continue buying the same things like food, gas or afford going out you will need more money.

In Europe, people typically calculate with an inflation rate of 2%-3%, mostly around 2.5%. In the US, people expect a higher inflation rate of over 3%, typically 3.3% (if taking the average of the last 100 years of all inflation rates).

So, when you calculate Coast FIRE number, as well as your FIRE number, be sure to take inflation into account.

FREE Coast FIRE Calculator

Use our free Coast FIRE Calculator to calculate coast fire number in minutes.. Find out how much you need to save and invest to reach your Coast FIRE number early on in life — and when your retirement account will be fully funded. We’ve also included a line-by-line breakdown of the exact calculation.

FAQ: Coast FI Explained

What Is the Biggest Coast FI Pitfall?

The biggest pitfall of Coast FI is relying too heavily on assumptions about future market returns and inflation. Future performance is never guaranteed — long market downturns or periods of low returns can delay or even derail your Coast FI timeline. When you calculate Coast FIRE number, make it a habit to check in regularly and see whether your plan is still moving in the right direction.

What Happens After You Reach Coast FI?

Once you hit Coast FI, you can reduce work hours, switch to a passion-driven job, or even take mini-retirements. Your investments continue compounding toward your FIRE goal—without constant saving pressure. But because of the Coast FI pitfall mentioned above, it’s crucial to review your plan regularly and adjust your contributions or expenses when market conditions change.

Is Coast FI Realistic for Families?

Yes! Many families reach Coast FI by front-loading their savings early—before kids or during dual-income years. Once their investments can grow on their own, they shift to part-time work, freelancing, or flexible jobs that fit family life.

How Much Money Do You Need for Coast FI?

It depends on your lifestyle, age, and target retirement age. Most people’s Coast FI number is about 25–40% of their total FIRE number, depending on expected growth rate and years until retirement. So, after you calculate Coast FIRE number, be sure to review your numbers regularly. If your FIRE number changes, you’ll need to adjust your Coast FIRE number as well.

When you walk away today with at least one new idea to improve your financial journey, I’d love to show you more in the next post. If you haven’t already, you can join our community so you don’t miss any new releases. Simply subscribe to the newsletter below in the green footer.

Now, I’d love to hear from you: what do you struggle with most when calculating your Coast FIRE number? Let me know in the comments below!

In our next blog post you can read everything you need to know about how you should invest to reach financial freedom.

Title image source: Jeremy Bishop on Unsplash