Coast FIRE Calculator

On this page, you’ll find a Coast FIRE calculator tool designed to show you when you can safely stop making contributions to your investments and let compounding do the heavy lifting. Unlike the general FIRE calculator that focuses only on the point at which you can fully retire, the Coast FIRE calculator highlights the moment when your portfolio is large enough to grow to your retirement goal without any further savings.

It allows you to test different scenarios and find out how soon you can shift your focus from saving to simply maintaining your lifestyle while compounding takes care of the rest.

What does this calculator do?

The Coast FIRE calculator takes several inputs — your age, retirement age target, current portfolio size, contributions, expected real return, annual spending needs, and withdrawal rate — and runs a projection. It calculates:

Your nest egg target: how much money you’ll need at retirement, based on your desired spending and withdrawal rate.
The present value needed today to coast: what you’d need right now (if you stopped contributing) for compounding alone to carry you to your target.
Your shortfall or surplus: whether you’re already at CoastFIRE or how much further you need to go.
Your Coast date: the age and calendar date at which you’ll hit the coast threshold, meaning you can stop saving and let growth do the rest.

How to use the Coast FIRE calculator

Currency code
- Enter your preferred currency (e.g., AUD, USD, EUR).
Current age
- Enter your current age. This helps the calculator determine how many years of compounding are available until retirement.
Target retirement age
- When would you ideally like to retire? This sets your timeline.
Current portfolio
- The current value of your investments earmarked for FIRE. Do not include your emergency fund or short-term savings.
Monthly contribution (until you hit coast)
- How much you are saving monthly until you’ve hit CoastFIRE. After reaching the coast threshold, the model assumes you stop contributions.
Expected real return (%/yr)
- Your estimated annual return after inflation. A safe range is usually 3–5%.
Desired annual spending in retirement
- How much you plan to spend each year once retired, in today’s dollars.
Withdrawal rate (%/yr)
- Typically 3.5-4% is used. This determines your required nest egg size.
Optional controls
- Toggle the chart view on/off.
- Reset the calculator to default example values.
- Export results to CSV for further analysis.

How to interpret the results

Years to retirement: how long until your chosen retirement age.
Target nest egg at retirement: the size of portfolio you’ll need to support your spending.
PV needed today to coast: the amount you’d need invested today to stop contributing immediately.
Shortfall or surplus: whether you’re above or below that figure.
At Coast today?: a quick yes/no answer.
Months/years until coast: if you’re not there yet, how long contributions will take to get you there.
Estimated Coast date: the actual calendar date you’re projected to reach CoastFIRE.

The graph shows your portfolio balance over time against the coast threshold curve. The point at which the two lines meet is your coast date.

Tips for using the calculator effectively

Test different return rates: Use both optimistic and conservative numbers (e.g., 3% and 5%) to see how sensitive your plan is.
Adjust your spending assumptions: A slightly lower retirement lifestyle cost can drastically reduce your required nest egg.
Experiment with retirement age: Delaying retirement by a few years can significantly reduce how much you need to save today.
Use it for flexibility: Reaching CoastFIRE doesn’t mean you must stop contributing. It simply gives you freedom you could scale back if you choose.
Export the data: The CSV download lets you model in spreadsheets and run your own sensitivity tests.

Contact me if you have any questions