Coast FIRE — The Idea
Grow what you have while working covers today's bills
Coast FIRE is the point where your existing portfolio will grow into your retirement target on its own, without another dollar of contributions. You still work to cover current expenses, but the saving-for-retirement part is finished.
How the calculation works
Start with the portfolio you will need at retirement. Then work backwards to find what balance today would grow into that figure by then at your assumed return.
Someone who needs $1.5 million at 65 and assumes 7% would need roughly $375,000 at age 45, since that amount roughly quadruples over twenty years.
If your current balance exceeds that figure, you have reached coast FIRE for that target and timeline.
- Coast FIRE means the existing balance grows into the target unaided.
- You still work to cover current living expenses.
- It arrives much earlier than full financial independence.
- The number depends heavily on your assumed return.
- Reaching it creates career flexibility rather than retirement.
Why it appeals to people
Full financial independence can take decades, which is a long time to sustain motivation. Coast FIRE arrives much sooner and provides a real change in circumstances.
Once you hit it, you can take a lower-paying job you enjoy more, reduce hours, or stop worrying about retirement savings entirely.
The psychological shift matters too. Knowing your retirement is handled removes a persistent background anxiety even if your daily life looks unchanged.
The assumption risk is real
Coasting depends entirely on the return you assumed. If you calculate your coast number at 8% and markets deliver 5%, you will arrive well short.
Using a conservative rate makes the coast number larger and the plan considerably safer. The difference between 5% and 8% in that calculation is substantial.
Recheck annually against your actual balance. If you have fallen behind the path, resuming contributions for a while is a straightforward correction.
Coasting does not mean ignoring
The portfolio still needs to stay invested appropriately and stay diversified. Coasting is about contributions, not about attention.
You also still need an emergency fund, since the whole arrangement depends on never having to raid the retirement portfolio early.
And your spending still needs to be covered by work. Coast FIRE says nothing about current cash flow, only about retirement funding.
Where it fits between the other milestones
Coast FIRE typically arrives well before full financial independence and after you have built a meaningful balance, which for many people is somewhere in their late thirties or forties.
It sits naturally after the emergency fund and high-rate debt are handled, since both of those protect the portfolio you are about to stop feeding.
Reaching it does not require any change in behavior. Many people pass coast FIRE and keep contributing, simply because the habit is running and earlier retirement appeals to them.
The value is in knowing where you stand. A career decision looks different when retirement is already funded than when it depends on the next twenty years of contributions.
How to use this calculator for it
This tool is built around financial independence rather than coasting, but you can approximate the calculation easily.
Work out your retirement target, then run a projection with zero monthly contributions and vary the starting balance until the ending figure matches.
That starting balance is your coast number for that timeline and rate. Compare it against what you actually have.
Run it at two different rates as well, since the gap between an optimistic and a conservative coast number tells you how much margin you are relying on.
Try these inputs
- Coast check: $375,000 start, no contributions, 7%, 20 years
- Conservative version: same balance at 5% for 20 years
- Your number: vary the starting balance until it hits your target