Coast FIRE Calculator: How Much to Save Now So You Can Stop Later

Coast FIRE means saving aggressively early, hitting a target number, then stopping retirement contributions entirely and letting compound interest do the rest.

At 30 years old, you need $172,000 invested to coast to $1,500,000 by age 65, assuming 7% real annual returns. After hitting $172,000, you never contribute another dollar to retirement. The portfolio does it automatically over 35 years.

This is the power of compound interest given enough time.

The Coast FIRE Formula

Coast FIRE Number = FIRE Number / (1 + r)^n

Where:

• FIRE Number = your retirement target (annual expenses / withdrawal rate)
• r = expected annual real return
• n = years until retirement

Example:

• Target: $1,500,000 at retirement
• Years until retirement: 35 (age 30, retiring at 65)
• Expected annual return: 7%

Coast Number = $1,500,000 / (1.07)^35 = $1,500,000 / 10.68 = $140,500

Once you have $140,500 invested, you can stop contributing and reach $1,500,000 by 65.

Coast FIRE Numbers by Age

Target retirement portfolio: $1,500,000. Assumed return: 7% annually.

| Current Age | Retiring at 65 | Coast FIRE Number | |------------|---------------|-----------------| | 25 | 40 years | $99,000 | | 28 | 37 years | $121,000 | | 30 | 35 years | $140,500 | | 32 | 33 years | $163,000 | | 35 | 30 years | $197,000 | | 38 | 27 years | $233,000 | | 40 | 25 years | $267,000 | | 42 | 23 years | $308,000 | | 45 | 20 years | $387,000 |

The earlier you start, the lower the Coast number. A 25-year-old needs $99,000. A 45-year-old needs $387,000 to reach the same destination.

What Happens After You Hit Coast FIRE

After hitting your Coast number, you stop contributing to retirement accounts. Your investment accounts grow on their own. You redirect all the money that was going toward retirement investments.

Where that money goes defines the Coast FIRE lifestyle:

Option 1: Downshift to lower-stress work. Take a job you enjoy more but pays less. Stop sacrificing career satisfaction for a salary you no longer need to max out.

Option 2: Work fewer hours. Go part-time or freelance. Cover living expenses without needing to save anything.

Option 3: Take a career break. Travel, care for family, start a project. Your portfolio is already on autopilot.

Option 4: Continue accumulating. If you hit Coast at 30 and keep contributing, you reach full FIRE earlier and at a higher number.

The Calculation That Changes Everything

Why does Coast FIRE work so powerfully? The math of doubling.

At 7% real returns, money doubles roughly every 10 years (the Rule of 72: 72 / 7 = 10.3 years).

$100,000 invested at age 25:

• Age 35: $200,000
• Age 45: $400,000
• Age 55: $800,000
• Age 65: $1,600,000

One investment, no further contributions, $1.6 million at 65. The only input was getting $100,000 invested early.

How Fast Can You Hit the Coast Number?

The Coast number is reachable faster than full FIRE because it is smaller.

At 28 with $0 saved, a $121,000 Coast target:

| Monthly Contribution | Years to Coast Number | |--------------------|-----------------------| | $1,000 | 8.5 years (Coast at 36) | | $1,500 | 6 years (Coast at 34) | | $2,000 | 4.7 years (Coast at 33) | | $3,000 | 3.2 years (Coast at 31) |

Assumes 7% return during accumulation phase.

Hitting $121,000 in 3-5 years is achievable for many dual-income households in their late 20s. Full FIRE in that same timeframe is not.

The Coast FIRE Risk

Coast FIRE has one critical vulnerability: time. It requires you to not touch the portfolio for decades. That means:

Market risk over a long period. Thirty-five years includes multiple recessions and bear markets. The 7% real return is a long-run average, not a guarantee in any specific decade.

Inflation risk. Your $1,500,000 target in 2026 dollars may need to be $2.5 million in 2061 dollars if inflation runs higher than expected. Build a buffer into your retirement target.

Career risk. Downshifting after Coast FIRE means lower Social Security benefits from reduced earnings in later years. Model this if Social Security is part of your retirement plan.

Life changes. Divorce, health issues, or children can change the retirement number. What was a Coast number at 30 may become inadequate at 40.

Coast FIRE vs Barista FIRE

The two strategies overlap but differ in how income is handled:

Coast FIRE: You stop contributing to retirement. Your income covers living expenses but not savings. Work is optional for financial reasons.

Barista FIRE: You draw from your portfolio partially. Work covers a portion of living expenses and the portfolio covers the rest. You need more invested than Coast (some withdrawals happening now) but less than full FIRE (income offsets some withdrawals).

Coast FIRE is simpler. Barista FIRE is more flexible for people who retire in their 40s when Social Security is decades away.

Frequently Asked Questions

Does Coast FIRE account for Social Security?

Not automatically. If you will receive Social Security at 65 or 67, your actual FIRE number is lower because Social Security replaces part of the portfolio income needed. Subtract your estimated Social Security benefit from annual expenses before calculating the FIRE number. A $2,000/month Social Security benefit ($24,000/year) reduces a $60,000 expense burden to $36,000, cutting the FIRE number from $1.5M to $900,000.

What if I want to retire before 65?

Coast FIRE can target any retirement age. Change the "n" in the formula to match. At 30 targeting retirement at 50 (20 years): Coast Number = $1,500,000 / (1.07)^20 = $1,500,000 / 3.87 = $387,500. Significantly higher Coast number but achieves financial independence 15 years earlier.

Can I count home equity in my Coast FIRE number?

Paid-off home equity can be counted if you plan to downsize or relocate in retirement and access the equity. A $300,000 home you plan to sell at 65 reduces the portfolio needed by $300,000. Most pure Coast FIRE calculations use only investable assets (retirement accounts plus taxable brokerage).