There is a financial independence concept gaining popularity called Coast FI.
The idea is simple: save enough early in life that, even if you stopped contributing to retirement altogether, your existing investments could theoretically grow enough to fund retirement on their own.
In other words, you reach a point where compound growth is expected to do most of the remaining work.
Suppose a 35-year-old wants to have $1.8 million by age 65. If they already have roughly $240,000 invested and that money earns an average annual return of 7%, it could theoretically grow to about $1.8 million over the next 30 years without another contribution. That basic calculation is at the heart of Coast FI.
It is easy to understand why the idea is appealing.
Someone who reaches that milestone may feel less pressure to maximize retirement savings every year. They might have more flexibility to change careers, start a business, work fewer hours, spend more while raising children, or direct money toward other goals.
And Coast FI highlights a broader financial truth that is worth emphasizing:
The earlier you save, the more time gets to do the heavy lifting.
But there is a major difference between saying the math is useful and saying the number is precise.
The Formula Is Simple. Your Life Is Not.
The Coast FI calculation depends on several assumptions, and over a 20-, 30-, or 40-year period, relatively small changes can produce very different outcomes.
Start with the retirement target itself.
If someone says they want $1.8 million at age 65, what does that really mean?
Is the goal literally to have $1.8 million in the future, or to have the purchasing power of $1.8 million today?
At 2.5% annual inflation, it would take roughly $3.8 million in 30 years to equal the purchasing power of $1.8 million today.
Then there is the assumed investment return.
A 7% average return may be reasonable for an illustration, but markets do not produce a neat 7% every year. Long-term returns could be lower. A different investment allocation could produce different results. And poor returns along the way could leave the portfolio well behind the original projection.
The original Coast FI calculation also assumes you know what retirement will eventually cost.
That may be a difficult assumption to make at 30 or 35.
Marriage, children, housing decisions, career changes, healthcare expenses, taxes, supporting family members, and changes in retirement age can all materially affect the amount someone ultimately needs. These uncertainties become especially important when the calculation is being made decades before retirement.
There is an interesting tension here:
The younger you are, the more powerful compounding can be—but the less certain you may be about what you are actually planning for.
Think of Coast FI as a Checkpoint
That does not mean Coast FI is a bad concept.
We think it is better viewed as a checkpoint rather than a finish line.
Instead of interpreting the number as:
“I never need to save for retirement again,”
a more useful takeaway may be:
“The saving I have already done has created significantly more flexibility.”
Even after reaching a theoretical Coast FI number, continuing to save may still make sense.
Employer matches are difficult to ignore. Roth IRA or Roth 401(k) contributions may provide valuable tax diversification. HSA contributions can be especially attractive. Higher-income years may also be some of the easiest times to build additional retirement margin.
Future contributions do not just increase the eventual account balance.
They also provide protection against imperfect assumptions.
The Bigger Lesson
Coast FI is appealing because it tries to reduce retirement planning to one number.
Real retirement planning rarely works that way.
Still, the concept points to something very important.
Saving early can dramatically change the trajectory of a financial plan.
Someone who waits until later in life may need much larger annual contributions to reach the same goal. Someone who starts earlier gives each dollar more time to potentially compound.
That does not mean everyone needs to save as aggressively as possible in their 20s and 30s. Financial planning is about balancing today with tomorrow.
But it does mean that early saving can create something even more valuable than a larger future account balance:
options.
At Hanover Advisors, we believe the goal is not simply to accumulate the largest possible portfolio or identify the exact age when you can stop contributing.
The goal is to build enough financial strength that, over time, you have greater flexibility in how you work, spend, and eventually retire.
Coast FI may not tell you exactly when your retirement is fully funded. But it is a powerful reminder that the earlier you put your money to work, the longer your money has the opportunity to work for you.