Coast Fire Calculator

Current Savings and Investments:

Annual Expenses in Retirement:

Years Until Retirement:

Coast FIRE is the milestone where your investments, left untouched, should grow into a full retirement fund by the time you stop working. The Coast Fire Calculator tells you the size of that milestone for your own numbers, what your current savings could become by retirement, and how much more you need to reach the coasting point.

Unlike some versions, this calculator lets you set your own timeline. You enter the years remaining until retirement, and it uses a 7 percent assumed annual return to work backwards from your retirement spending target to the amount you need invested today.

This guide explains the target, the assumed return, and each of the three results in turn. Two worked examples cover a long 25-year horizon and a shorter 15-year one, showing how dramatically the required amount changes with time.

Your Full Retirement Target Comes First

Every Coast FIRE figure begins with the full amount you would need to retire outright, estimated here as 25 times your expected annual retirement expenses. Spend $52,000 a year in retirement and the target is $1,300,000.

That target rests on the familiar 4 percent guideline, which treats a portfolio of 25 times spending as capable of supporting that spending over a long retirement. It is a planning convention rather than a law of nature, but it gives the calculation a consistent anchor.

Honest expenses are essential. Understating your expected spending shrinks the target and flatters the result, so build the figure from the retirement life you actually intend to fund, including healthcare and housing as they will really be.

Working Backwards at 7 Percent

The calculator assumes investments grow at 7 percent a year, a widely used long-term planning figure for a growth-oriented portfolio after inflation. It divides your full target by that growth compounded over your years until retirement.

The result is your Coast FIRE number: the amount that, invested today and never added to, would arrive at the full target exactly when retirement begins. More years means more compounding, so the number falls quickly as the horizon lengthens.

Because the return is fixed in this tool, your timeline is the lever to experiment with. Pushing retirement five years later can cut the required amount dramatically, which is worth knowing before you assume the milestone is out of reach.

The Gap: Additional Savings Needed

The third result compares your current savings with the Coast FIRE number and shows the difference, floored at zero. That gap is the most actionable figure on the page, because it converts an abstract milestone into a concrete savings target.

A gap is not a failure; it is a work order. Spread across the years until you want to reach coasting, it becomes a monthly contribution target you can test against your budget.

The second result keeps the gap in perspective by projecting your current savings forward at the same 7 percent. Watching today's balance grow toward the full target on paper is often the motivation that closes the gap in practice.

How to Use the Coast Fire Calculator

You need three figures: your current savings and investments, the annual expenses you expect in retirement, and the years remaining until you plan to retire. The calculator applies its 7 percent return assumption automatically.

Enter your current savings and investments, combining the accounts you intend to fund retirement with.
Enter your expected annual retirement expenses as a realistic yearly total in today's money.
Enter the years until retirement, counting from now to the age or date you plan to stop full-time work.
Press Calculate to see your Coast FIRE number, the projected value of your current savings at retirement, and the additional savings still needed.
Try a later retirement year to see how powerfully extra compounding time shrinks the amount you need today.

If the additional savings result reads zero, you have reached Coast FIRE at these assumptions. Keep the screenshot, recheck yearly, and enjoy the flexibility that milestone is designed to create.

Worked Example 1: A 25-Year Horizon

A saver in their late thirties is planning around a retirement 25 years away.

Step one: current savings are $90,000, entered into the first field.

Step two: expected retirement expenses are $52,000 a year, entered into the second field.

Step three: the horizon is 25 years, entered into the third field.

The calculator sets the full target at 25 times $52,000, which is $1,300,000.

Discounting that target back 25 years at 7 percent gives a Coast FIRE number of about $239,524.

Projecting the current $90,000 forward 25 years at 7 percent gives about $488,469 at retirement.

The additional savings needed reads about $149,524, the gap between today's balance and the Coast FIRE number.

Worked Example 2: A 15-Year Horizon

An older saver with a shorter runway runs the same style of calculation.

Step one: current savings are $210,000, entered into the first field.

Step two: expected retirement expenses are $46,000 a year, entered into the second field.

Step three: the horizon is 15 years, entered into the third field.

The calculator sets the full target at 25 times $46,000, which is $1,150,000.

Discounting that target back 15 years at 7 percent gives a Coast FIRE number of about $416,813.

Projecting the current $210,000 forward 15 years at 7 percent gives about $579,397 at retirement.

The additional savings needed reads about $206,813, showing how a shorter horizon demands a much larger amount invested today.

Why the Horizon Changes Everything

Compounding is exponential, so time is not just one input among three; it is the engine of the whole strategy. Each extra decade at 7 percent roughly doubles what a given balance becomes, which halves what you need to set aside today.

This is why Coast FIRE is primarily a young saver's milestone. Someone with 30 years of growth ahead can coast from a surprisingly modest balance, while someone 10 years out needs something much closer to the full target already invested.

The practical lesson cuts both ways: starting the coasting clock early is enormously valuable, and delaying retirement by even a few years is one of the strongest levers available to someone whose gap looks stubborn.

Limits of a Fixed 7 Percent Assumption

Real returns arrive unevenly, with strong decades and flat ones, and the sequence matters more the closer retirement gets. A fixed 7 percent line is a planning average, not a path your portfolio will actually follow year by year.

Portfolio mix changes the honest assumption too. A conservative portfolio heavy in bonds would normally be modelled lower, while the expenses target itself can shift with health, housing, and family changes over decades.

Use this calculator as the quick, consistent check it is designed to be. For decisions like leaving a career, revisit the numbers with more detailed planning and, ideally, professional advice that can model taxes, pensions, and withdrawal order.

Remember that every online estimate is a planning aid, not a final answer. Rules, prices, and personal circumstances change, and the figure you see today is a snapshot based on the details you provided at this moment rather than a promise about the future.

If the result surprises you, that is usually a sign to slow down and review each input carefully. Surprising results often come from one misunderstood field, such as entering a yearly figure where a monthly figure was expected, or the other way around.

Many people find it useful to share their results with a partner, family member, or trusted adviser before acting. A second pair of eyes can spot an unrealistic assumption quickly and can help you decide which scenario deserves the most attention.

Small changes compound. Adjusting one input by a modest amount and watching how the outputs respond teaches you which factors drive the result most strongly, and that understanding is often more valuable than the headline number itself.

Revisit your estimate whenever something material changes in your life, such as a new job, a move, a rate change, or a revised deadline. An estimate that was accurate three months ago may no longer reflect the decision you are about to make today.

Where money or health is involved, treat the output as the start of a conversation rather than the end of one. Use it to prepare better questions for a qualified professional who can review your full circumstances before you commit to a course of action.

Finally, keep your expectations grounded. A careful estimate built on honest inputs will serve you far better than an optimistic guess, even when the honest answer is less exciting, because good decisions start from a clear picture of where you stand right now.

Accuracy matters more than speed with any estimate. Before you rely on a result, double-check that every number you entered matches your real documents, statements, or plans, because even a small typing mistake can shift the outcome in a meaningful way.

It also helps to run the same scenario more than once with slightly different assumptions. Comparing a cautious case, a middle case, and an optimistic case shows you the range of outcomes you might face, which is far more useful than trusting a single figure on its own.

Keep a simple record of the results you get. Writing down the inputs you used and the date you ran the estimate makes it easy to repeat the calculation later and to see how your situation changes over time as balances, prices, and deadlines move.

Tips for Getting the Most From the Coast Fire Calculator

Count every year honestly because the horizon is the most powerful input in the entire calculation.
Build retirement expenses from your real plans, including healthcare, rather than copying today's spending blindly.
Treat the gap as a monthly savings target by spreading it across the years until you want to reach coasting.
Recheck after market moves since a strong year can pull you to the milestone sooner than contributions alone would.
Test a retirement date two or three years later to see how much relief a small delay provides.
Keep contributing after reaching the number to build margin against returns that fall short of 7 percent.
Include all retirement-bound accounts in your savings figure so the gap reflects your true position.
Revisit the plan after life changes such as children, a home purchase, or a career shift, since each moves the target.

Frequently Asked Questions

1. What is the Coast FIRE number?

It is the amount you need invested today so that growth alone, at the assumed 7 percent return, carries it to your full retirement target by your retirement date.

Reaching it means further retirement contributions become optional rather than essential.

2. Why does this calculator assume 7 percent?

Seven percent is a common long-term planning assumption for a growth-oriented portfolio after inflation.

Fixing the rate keeps the tool simple and lets your timeline and expenses drive the comparison between runs.

3. How is the full retirement target set?

Your annual retirement expenses are multiplied by 25, following the 4 percent withdrawal guideline.

It is a planning benchmark, and your personal target may differ with pensions, rental income, or part-time work.

4. What does additional savings needed mean?

It is the gap between your current savings and your Coast FIRE number, shown as zero once you have reached the milestone.

Think of it as the amount left to invest before growth can take over the job.

5. What if my projected value exceeds the full target?

That means your current savings, growing at 7 percent with no additions, would overshoot the target by retirement.

You are not only coasting but ahead of schedule, which gives you options around retiring earlier or spending more.

6. Does reaching Coast FIRE mean I can stop working?

No. It means retirement is funded on paper, but you still need income for living costs between now and retirement.

The benefit is flexibility: part-time work or a lower-paid passion career can cover those costs.

7. How does a longer horizon lower the number?

More years of compounding do more of the work, so less starting capital is required.

At 7 percent, money roughly doubles every ten years, which is why the number falls so quickly as years are added.

8. Should I include my pension or Social Security?

Those income sources reduce the spending your portfolio must cover, so you can reflect them by lowering the annual expenses you enter.

That produces a smaller, more accurate target for portfolio-based saving.

9. Can couples run one calculation together?

Yes. Combine both partners' savings and use your shared expected retirement expenses and the relevant retirement date.

The results then describe the household's coast position.

10. What if my expenses estimate changes?

Re-run the calculator. Higher expected spending raises both the target and the Coast FIRE number, while lower spending reduces them.

Annual rechecks keep the milestone aligned with the life you are actually planning.

11. Is 25 times expenses right for everyone?

It is a widely used starting point, but early retirees, generous pensions, or unusual health costs can justify a different multiple.

Use it as the default and adjust your thinking if your circumstances are clearly atypical.

12. How often should I recalculate?

Once a year suits most people, plus after major changes to savings, expenses, or retirement timing.

Regular checks turn the milestone into something you track rather than something you guess at.

13. What return do conservative portfolios use?

Lower than 7 percent, often in the 4 to 5 percent range after inflation.

If your portfolio is conservative, treat this calculator's results as optimistic and keep a larger margin.

14. Can I reach Coast FIRE and still save?

Absolutely. Extra contributions after the milestone either pull full retirement closer or build protection against weak returns.

Coasting is permission to ease off, not an instruction to stop.

15. Does the calculator store my financial details?

No. The three numbers you enter are processed in your browser only.

Nothing is saved or transmitted, so you can test scenarios privately and freely.

CONCLUSION

Coast FIRE turns retirement saving into a reachable milestone with a date attached. The Coast Fire Calculator shows the amount you need invested today, what your current savings could grow into by retirement, and the exact gap left to close.

Run it with honest expenses and your real timeline. If a gap remains, you now know its size and can plan contributions against it. If it reads zero, you have earned the flexibility to reshape your working life while compound growth finishes the job.