Coast FIRE Calculator

How to use this calculator

Enter your current age, target retirement age, current savings, annual retirement expenses, expected return, and inflation rate. Click Calculate Coast FIRE.

The calculator shows your Coast FIRE number (how much you need saved today to stop contributing), your full FIRE number, the gap between your current savings and the Coast FIRE threshold, and a chart showing two growth trajectories: if you had exactly the Coast FIRE number right now versus your actual current savings.

Annual Retirement Expenses should be in today’s dollars. The calculator adjusts for inflation internally. If you want to retire on $60,000 per year in today’s purchasing power, enter $60,000, not $60,000 × (1.03)^30.

Expected Return is your assumed annual nominal return. 7% is a standard assumption for a diversified equity portfolio. The calculator uses this with your inflation rate to compute the real return, which is what actually drives the Coast FIRE math.

The formula

Coast FIRE requires two calculations.

First, your full FIRE number:

Then, discount that future target back to today:

Why real return, not nominal?

The FIRE number is expressed in today’s dollars. Your annual expenses are $60,000 today, not $145,000 in 30 years. When you use real return in the Coast FIRE formula, both sides of the equation stay in today’s dollars and the math is cleaner.

If you used nominal returns, you’d need to express both the FIRE number and your current savings in nominal future dollars, which adds unnecessary conversion steps. Real return handles it in one.

The difference between 3.88% and 4% is small year-to-year. Over 30 years it’s $25,000 or more in the Coast FIRE calculation. Use the precise formula.

What actually changes when you hit Coast FIRE

Before Coast FIRE, missing a month of contributions costs real money. Every dollar not invested is a dollar that won’t compound for 20 to 30 years. Career pivots carry financial risk because they may reduce your savings capacity.

After Coast FIRE, that pressure disappears. Your invested money is doing the accumulation work. You just need to cover your living expenses. Work becomes optional in the sense that any job covering your bills is sufficient.

People who hit Coast FIRE commonly:

• Switch to lower-stress jobs they actually enjoy
• Take sabbaticals or extended travel
• Reduce to part-time hours
• Move to lower cost areas where they can work less

None of these require touching the portfolio. The portfolio grows on its own.

The psychological shift is significant. Before Coast FIRE, a job change that cuts income from $120,000 to $75,000 is financially risky. After Coast FIRE, the same job change is just a lifestyle choice. The portfolio no longer depends on your career choices.

How long it takes to reach Coast FIRE

Someone starting from zero who saves 30% to 35% of a $100,000 income typically hits Coast FIRE within 8 to 12 years, depending on return assumptions and target retirement expenses.

Here’s what Coast FIRE looks like across different scenarios (7% nominal, 3% inflation, targeting $60,000 per year in retirement):

The earlier you can hit Coast FIRE, the lower the required number. More time means less money needed today, because compounding has longer to work.

If you’re 25 and target retirement at 60, you only need $298,000 today to never invest another dollar and still retire with the full $1.5M. At 35 targeting the same retirement, you need $452,000. Those 10 years cost $154,000 in additional required savings.

Coasting vs fully stopping vs Barista FIRE

These three concepts get confused frequently because they overlap.

Full FIRE: Portfolio fully funds retirement. No work required. You need the full 25x FIRE number.

Coast FIRE: Your current savings will grow to the full FIRE number without more contributions. You still work to cover current expenses, but stop contributing to investments.

Barista FIRE: You work part-time for income. Your portfolio covers the gap between expenses and part-time earnings. Smaller portfolio required than full FIRE, and you don’t need to stop contributions since you’ve just reduced the required accumulation.

Coast FIRE is the most purely mathematical of the three. Once the growth projection hits the FIRE target, you’ve coasted. What you do with that status (work full-time, part-time, or not at all) is entirely up to you.

Many people discover they enjoy some form of work after hitting Coast FIRE. The difference is that it’s chosen rather than required.

You can also be in Coast FIRE and Barista FIRE simultaneously. If your portfolio is large enough to coast and your part-time income covers expenses, both conditions are met at once.

Risks and how to buffer them

You might underestimate retirement expenses. If your lifestyle costs more than projected, the FIRE number goes up and your Coast FIRE calculation was too optimistic. Review your spending target every few years and re-run the numbers.

Markets might underperform. Coast FIRE assumes your real return holds constant. The 2000s were a lost decade for US equities: real returns from 2000 to 2010 were roughly negative 1% annually for the S&P 500. A decade like that near the end of your coasting period would set you back significantly.

Buffer recommendation: target a Coast FIRE number 15% to 20% above the minimum calculation. If the formula says $482,000, aim for $555,000 to $578,000. That buffer absorbs a few bad years without requiring you to resume heavy contributions.

Sequence risk near retirement still applies. Even if you coast successfully, a severe crash in the 3 to 5 years before your target retirement date matters. Having some allocation to bonds or cash as you approach retirement helps. You’ve spent decades building this portfolio; protecting it in the final years makes sense.

Inflation higher than expected. The formula uses your inflation assumption. If inflation runs at 5% instead of 3% for a decade, your real return drops by 2% per year. A $482,000 Coast FIRE portfolio at 7% nominal and 5% inflation has a real return of about 1.9% rather than 3.88%, and may not reach the full FIRE number by your target date.

Small contributions after Coast FIRE still help

“Coasting” doesn’t mean you have to stop investing entirely. If you’re earning enough to cover expenses and save a little, those contributions still compound for years.

The math: if your Coast FIRE portfolio is $482,000 and you add $500 per month for another 10 years at 7%, you’d have roughly $1.56M instead of the $1.5M target. That’s a $60,000 buffer from modest continued contributions.

Coasting gives you permission to stop. It doesn’t require you to.

Small ongoing contributions also act as insurance against underperforming markets. If returns are worse than expected, those contributions offset part of the shortfall. You end up with more flexibility and more margin for error.

Coast FIRE and career decisions

The most practical use of reaching Coast FIRE isn’t retirement. It’s career optionality.

Once you’ve hit the number, you can afford to take a lower-paying job you actually like. You can start a business that won’t pay you well for the first two years. You can take 6 months unpaid leave without permanently derailing retirement. You can move to a city with fewer high-paying opportunities because the career income pressure is gone.

These choices don’t require touching the portfolio. They’re funded by the security that comes from knowing the portfolio is already doing the long-term work.

A 35-year-old engineer who reaches their Coast FIRE number has roughly 20 to 25 years of compounding ahead before standard retirement age. Even with mediocre market returns, the portfolio reaches the FIRE number. A job change at that point is financially inconsequential in the long run.

This is the real value proposition of Coast FIRE. Most people who pursue it don’t actually plan to stop working. They plan to work differently, with less financial anxiety driving their choices.

Coast FIRE numbers at different income targets

Here’s a reference table for Coast FIRE numbers at age 30, targeting retirement at 60, across different annual spending targets (7% nominal, 3% inflation):

If you want to retire on $40,000 per year and you’re 30, reaching $322,000 by 30 and stopping contributions completely still gets you to $1,000,000 by age 60. At a 30% savings rate on $80,000 income ($24,000/year), that $322,000 is reachable in roughly 9 to 11 years depending on starting savings.

Most people find these numbers surprisingly achievable once they see them concretely.

How to verify you’ve actually hit Coast FIRE

The Coast FIRE number from the formula is a mathematical target, but whether you’ve truly hit it depends on your assumptions holding up. Here’s how to verify.

Check the real return assumption. The formula uses real return ((1 + nominal) / (1 + inflation) - 1). At 7% nominal and 3% inflation, that’s 3.88%. If you’re using 5% real return in your calculation, your number is understated. Use the historical average: 3.5% to 4.5% real is a reasonable range for a diversified equity portfolio.

Check the FIRE number itself. If your spending estimate in retirement is off, the FIRE number is off, and the Coast FIRE number is off. Use your actual current spending as a base, adjust for retirement-specific changes (no commuting, no work wardrobe, potentially lower housing costs), and make sure you’ve included healthcare explicitly.

Add a buffer. The formula gives the minimum. Aiming for 115% to 120% of the calculated number gives you a margin for below-average returns, higher-than-expected inflation, or spending underestimates. This buffer is the difference between “technically hit the number” and “can actually stop contributing with confidence.”

Recheck every 3 to 5 years. Return assumptions and retirement spending targets change. A number you calculated at 30 may need updating at 35 if your desired retirement lifestyle has evolved. The Coast FIRE calculation should be a living estimate, not a one-time target.

Once you’ve verified the number with realistic assumptions and an appropriate buffer, you can genuinely stop contributing and shift your career toward what you actually want to be doing. That’s the practical payoff of the Coast FIRE calculation.