How Coast FIRE Works
Coast FIRE means reaching a point where the portfolio may be able to grow into a full retirement target without needing heavy new contributions forever. This page shows both the true coast threshold today and the projected portfolio if you keep contributing until your chosen age.
Your full FIRE number still comes from spending and withdrawal rate. The first result tells you what you would need invested today to stop contributing immediately. The projected portfolio and status show what happens if you keep saving until the coast age you entered.
If you want to model the impact of your income and spending habits first, try the Savings Rate Calculator. If you want to model continued investing instead of coasting, try the FIRE Calculator. If you want to estimate the portfolio your spending supports, use the 4% Rule Calculator. If you want to project pure growth over time, try the Compound Interest Calculator. If you want to compare starting sooner versus later, open the Started Investing Earlier Calculator.
What This Calculator Is Good For
- Checking whether your current portfolio is already large enough to Coast FIRE
- Estimating your Coast FIRE number with a simpler real-return assumption
- Estimating how far away you are from the point where new contributions become optional
This is especially useful if you are considering a lower-pressure job, a career break, part-time work, or just want to know whether continuing to save aggressively still changes the outcome meaningfully.
How To Use The Calculator
Use Coast FIRE as a pressure test on future flexibility, not as permission to assume the hard part is already over.
- Enter your current age and the age when you want new contributions to become optional.
- Add the portfolio you already have and the contribution you still expect to make.
- Enter a retirement spending number you can defend, not a wishfully low one.
- Test a conservative return and withdrawal rate before you trust a green result.
- Compare the true coast number with the projected portfolio at your coast age.
Method And Assumptions
The calculator estimates a future FIRE number from retirement spending and withdrawal rate, then discounts that target back to today using the return assumption and years remaining. That discounted result is the true Coast FIRE number today.
The projected portfolio adds ongoing monthly contributions until your coast age, which helps show whether you are already there, close, or still meaningfully behind. It does not model taxes, fees, changing spending, income interruptions, or uneven return sequences.
This is not financial advice. Coast FIRE is unusually sensitive to return assumptions because the whole concept depends on long-run compounding doing a lot of work.
Real Example
If your retirement spending target is 360,000 per year and your withdrawal rate is 4%, your future FIRE number is 9,000,000. If you are 35 and want to coast at 45, the calculator estimates whether your portfolio at 45 could grow to that future target by the retirement age assumption implied in the model.
If a lower return assumption removes the coast status, the plan is not broken; it is just less robust than the optimistic case suggested.
How To Interpret Results
The true coast number answers: “How much would I need invested right now if I never added another serious contribution?” The projected portfolio answers: “Where do I likely land if I keep going until the age I chose?” Those are different questions, and reading them together is the whole point.
Common Mistakes And Limitations
Common mistakes include using a generous return, underestimating future spending, or treating Coast FIRE as if it means risk has disappeared. A long coasting period leaves plenty of time for returns, taxes, and lifestyle costs to surprise you.
Run a lower-return case and a higher-spending case before making real decisions off the output.
FAQ
Does Coast FIRE mean I can stop investing?
Not automatically. It means the assumptions suggest your portfolio could coast, but risk remains.
Why is return assumption so important?
Because the model relies on future compounding over many years.
Does this include inflation?
It treats the annual return as a real-return style planning assumption. Keep spending and returns consistent.