Coast FIRE Case Study: How Sarah & Mike Hit Their Coast Number at 35
Real Coast FIRE example with actual numbers. See how this couple saved $250K by age 35 and never had to save for retirement again. Includes calculator and step-by-step breakdown.
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Coast FIRE Case Study: Meet Sarah & Mike
Sarah (35) and Mike (36) are a married couple living in Austin, Texas. They just hit their Coast FIRE number of $250,000 in retirement savings—which means they never have to save for retirement again.
Let's break down exactly how they did it, what their numbers look like, and what their lives look like now in "coast mode."
Their Starting Point (Age 25)
Sarah (Age 25)
| Category | Details |
|---|---|
| Job | Marketing coordinator |
| Income | $48,000/year |
| Retirement savings | $0 |
| Student loans | $28,000 |
| Living situation | Roommates |
Mike (Age 26)
| Category | Details |
|---|---|
| Job | Software developer |
| Income | $65,000/year |
| Retirement savings | $5,000 (from internships) |
| Student loans | $15,000 |
| Living situation | Small apartment |
Combined Starting Point
| Category | Amount |
|---|---|
| Total income | $113,000 |
| Retirement savings | $5,000 |
| Debt | $43,000 |
They weren't starting from privilege—just two regular people with college debt and entry-level jobs.
The 10-Year Journey to Coast FIRE (Ages 25-35)
Phase 1: Debt Elimination (Years 1-2)
Strategy: - Lived in a modest 2-bedroom apartment - Combined expenses: $2,500/month - Aggressively paid off student loans - Started 401(k) contributions to get employer match only
Results after 2 years:
| Category | Amount |
|---|---|
| All debt paid off | ✅ |
| Emergency fund | $15,000 |
| Retirement savings | $35,000 |
Phase 2: Aggressive Saving (Years 3-7)
Once debt-free, they shifted to maximum retirement contributions:
Annual Contributions:
| Account Type | Contribution |
|---|---|
| Sarah's 401(k) | $19,500 |
| Mike's 401(k) | $19,500 |
| Sarah's Roth IRA | $6,000 |
| Mike's Roth IRA | $6,000 |
| **Total** | **$51,000/year** |
Income increases:
| Person | Income by Year 7 | Details |
|---|---|---|
| Sarah | $68,000 | Promotions |
| Mike | $95,000 | Job switches |
| **Combined** | **$163,000** |
Lifestyle: - Still lived modestly (~$4,000/month expenses) - One used car, one bike commuter - Cooked at home, budget travel - No kids yet (planned for post-Coast FIRE)
Results after 7 years (age 32):
| Account Type | Balance |
|---|---|
| Retirement savings | $185,000 |
| Taxable brokerage | $40,000 |
Phase 3: Final Push (Years 8-10)
The home stretch:
| Category | Amount |
|---|---|
| Combined income | $180,000 |
| Maxed retirement accounts | $52,000/year |
| Added HSA contributions | $7,300/year |
| **Total savings** | **$59,300/year** |
Results at age 35:
| Account Type | Balance |
|---|---|
| 401(k)s | $320,000 |
| Roth IRAs | $75,000 |
| HSA | $25,000 |
| Taxable brokerage | $80,000 |
| **Total** | **$500,000** |
But their Coast FIRE number was only $250,000—they actually over-saved!
Calculating Their Coast FIRE Number
Here's the math they used at age 25:
Their Retirement Goals
| Category | Value |
|---|---|
| Target retirement age | 65 |
| Years for money to grow | 40 years (from age 25) |
| Desired annual retirement spending | $75,000/year |
| Target retirement amount | $1,875,000 ($75,000 × 25) |
| Expected investment return | 7% per year |
The Coast FIRE Formula
Coast Number = Target Amount ÷ (1.07)^40
Coast Number = $1,875,000 ÷ 14.97 = $125,282
Their original Coast FIRE number was $125,000 at age 25.
But they recalculated every few years as circumstances changed:
| Age | Coast FIRE Number Needed | Reason |
|---|---|---|
| 25 | $125,000 | Original target |
| 30 | $177,000 | Less time to grow |
| 35 | $250,000 | Final goal, adjusted for higher lifestyle |
What Changed: Why They Kept Saving
Original plan: Hit $125K, stop saving, coast forever.
What happened: 1. Lifestyle inflation - They wanted a nicer retirement ($75K/year instead of $50K) 2. Kids - Decided they wanted 2 kids, needed separate college funds 3. Uncertainty buffer - Wanted extra cushion for market volatility 4. It wasn't hard - Saving became a habit, income kept growing
So they aimed for $250K instead and hit it at age 35.
Their Current Life in Coast Mode (Age 35)
What Changed
Before Coast FIRE: - Saved $5,000+/month aggressively - Stressed about every financial decision - Felt pressure to maximize income - Lived in small 2-bedroom apartment
After Coast FIRE: - Zero retirement contributions (except employer match) - Financial stress eliminated - Total freedom in career choices - Bought a modest 3-bedroom home
Their New Budget
Monthly income: $15,000 combined Monthly expenses: $7,500
| Expense Category | Amount |
|---|---|
| Mortgage (3-bed house) | $2,400 |
| Utilities | $250 |
| Groceries | $800 |
| Transportation | $400 |
| Insurance (health, home, auto) | $900 |
| Entertainment | $500 |
| Dining out | $400 |
| Travel fund | $800 |
| Kids expenses | $600 |
| Miscellaneous | $450 |
| **Total Expenses** | **$7,500** |
What happens to the other $7,500/month? - Emergency fund top-offs - Kids' 529 college savings: $1,000/month - Taxable brokerage (flexibility money): $2,000/month - Fun money / lifestyle: $2,000/month - Cash buffer: $2,500/month
They're still saving—but it's optional, not mandatory.
The Career Choices Coast FIRE Enabled
Sarah's Choice
| Aspect | Before Coast FIRE | After Coast FIRE |
|---|---|---|
| Job | Marketing manager at tech startup | Freelance marketing consultant |
| Income | $85,000/year | $60,000/year |
| Hours | 50+ hour weeks, high stress | 25-30 hours/week, work from home |
| Why the change | She wanted to be home with their newborn. The pay cut doesn't matter because retirement is handled. |
Mike's Choice
| Aspect | Before Coast FIRE | After Coast FIRE |
|---|---|---|
| Job | Senior developer at FAANG company | Developer at local nonprofit |
| Income | $140,000/year | $90,000/year |
| Work environment | High pressure, on-call rotations | 40-hour weeks, fulfilling work |
| Why the change | He wanted work that mattered more than money. Coast FIRE made that possible. |
Combined Impact
| Category | Result |
|---|---|
| Income change | Dropped from $225K to $150K |
| Lifestyle | Improved dramatically |
| Retirement status | Still 100% on track |
| Work-life balance | Achieved 30 years early |
Their Retirement Projection
The Math at Age 65
| Category | Value |
|---|---|
| Starting amount | $250,000 (their Coast number) |
| Years to grow | 30 years (from age 35 to 65) |
| Growth rate | 7% annually |
| **Growth calculation** | **$250,000 × (1.07)^30 = $1,903,273** |
Add in their extra savings:
| Account Type | Starting Balance | Grows to (at 65) |
|---|---|---|
| 401(k)s above Coast number | $170,000 | $1,295,000 |
| Roth IRAs | $75,000 | $571,000 |
| HSA | $25,000 | $190,000 |
Total projected at 65: $3,959,273
That's nearly $4 million in retirement savings—far beyond their original $1.875M target.
Monthly Retirement Income Projection
Using the 4% rule:
$3,959,273 × 4% = $158,371 per year
That's $13,198 per month from investments alone.
Add Social Security (~$4,500/month for a couple):
Total: ~$17,700/month in retirement
For a couple that spent $7,500/month in their 30s, this is an incredibly comfortable retirement.
What They Did Right
1. Started Early Age 25 is prime time for compound interest. Every dollar at 25 becomes ~$14 at age 65.
2. Prioritized Savings Over Lifestyle They could have afforded luxury cars and bigger apartments. They chose index funds instead.
3. Increased Contributions with Raises When Mike got raises, 50% went to savings, 50% to lifestyle. Never 100% to lifestyle.
4. Stayed Consistent Through Market Drops 2020 COVID crash? They kept contributing. 2022 bear market? Didn't flinch.
5. Educated Themselves Read books, followed FIRE blogs, understood compound interest deeply.
6. Supported Each Other Both were aligned on goals. No financial conflicts, just teamwork.
What You Can Learn From Their Strategy
If You're in Your 20s **Target:** Coast FIRE by 35
Action plan: 1. Start 401(k) contributions NOW (even 5%) 2. Increase by 1% every 6 months 3. Max out Roth IRA ($7,000/year) 4. Live below your means 5. Invest raises, not spend them
Goal: $200-300K by age 35
If You're in Your 30s **Target:** Coast FIRE by 40-45
Action plan: 1. Calculate your Coast FIRE number 2. Max 401(k) if possible ($24,500/year) 3. Aggressive 5-year savings sprint 4. Consider side hustles to accelerate
Goal: $300-400K by age 40
If You're in Your 40s **Target:** Coast FIRE by 50
Action plan: 1. Maximize all tax-advantaged accounts 2. Use catch-up contributions ($7,500 extra) 3. May need $500K+ to coast 4. Focus on increasing income
Different Coast FIRE Scenarios
Let's see how different incomes and ages affect Coast FIRE:
Scenario A: Single Person, Age 30, Modest Goals
| Category | Value |
|---|---|
| Current age | 30 |
| Retirement age | 65 |
| Years to grow | 35 |
| Desired spending | $40,000/year in retirement |
| Target amount | $1,000,000 |
| **Coast number** | **$94,000** ($1,000,000 ÷ (1.07)^35) |
Needs to save $94K by age 30 to never save again.
Scenario B: Couple, Age 40, Comfortable Goals
| Category | Value |
|---|---|
| Current age | 40 |
| Retirement age | 65 |
| Years to grow | 25 |
| Desired spending | $80,000/year in retirement |
| Target amount | $2,000,000 |
| **Coast number** | **$368,000** ($2,000,000 ÷ (1.07)^25) |
Needs $368K by age 40 to coast.
Scenario C: Late Starter, Age 45, Lean FIRE Goals
| Category | Value |
|---|---|
| Current age | 45 |
| Retirement age | 65 |
| Years to grow | 20 |
| Desired spending | $50,000/year in retirement |
| Target amount | $1,250,000 |
| **Coast number** | **$323,000** ($1,250,000 ÷ (1.07)^20) |
Needs $323K by age 45—challenging but doable with aggressive saving.
Coast FIRE Calculator
Use our free Coast FIRE calculator to determine YOUR coast number:
What you'll input: - Current age - Target retirement age - Desired annual retirement spending - Current retirement savings - Expected annual return (usually 6-8%)
What you'll learn: - Your exact Coast FIRE number - How much more you need to save - How long until you can coast - Projected retirement balance
Try the calculator above to see your personalized Coast FIRE plan!
Common Coast FIRE Mistakes to Avoid
Mistake 1: Not Accounting for Lifestyle Inflation If you plan for $50K/year but actually spend $75K in retirement, you'll run short. Build in a buffer.
Mistake 2: Stopping ALL Savings Too Early Coast FIRE means retirement is handled. But you still need: - Emergency funds - Kids' college funds - Home repairs - Healthcare before 65
Mistake 3: Using Unrealistic Return Assumptions 7% is historically accurate, but don't use 10% or 12%. Be conservative.
Mistake 4: Not Adjusting for Healthcare Healthcare from 55-65 can cost $15,000+/year. Factor this in if you plan to stop working early.
Mistake 5: Forgetting About Inflation $75,000 today ≠ $75,000 in 30 years. Either inflate your target or use real (inflation-adjusted) returns.
Frequently Asked Questions
Can I do Coast FIRE on a single income? Yes! It's harder but absolutely possible. You'll need to save aggressively in your 20s and 30s, but hitting $150-200K by age 35-40 can work.
What if the market crashes right after I hit Coast FIRE? This is a risk. Build a buffer—aim for 10-20% above your minimum Coast number. Or keep making small contributions until the market recovers.
Do I have to stop saving completely after Coast FIRE? No! Many people keep saving at a reduced rate. The point is you DON'T HAVE TO anymore. It's financial freedom, not a mandate to stop.
What about kids and college? Coast FIRE is separate from college savings. You'll need dedicated 529 plans. Sarah & Mike save $1,000/month for their kids' college.
Can I Coast FIRE and still retire early? Yes! Coast FIRE gets you to "normal" retirement age. But if you keep saving optional amounts, you can retire even earlier. It's your choice.
What happens if I want to un-retire? Perfect! Coast FIRE gives you flexibility. If retirement is boring, you can work part-time or freelance—because your retirement is already secure.
The Bottom Line
Coast FIRE is the most achievable form of financial independence for most people. You don't need $2-3 million—you need $150-300K in your 30s or 40s.
Sarah and Mike's story shows it's possible: - Started with debt - Saved aggressively for 10 years - Hit Coast FIRE at 35 - Now live life on their terms
Your path will be different, but the principles are the same: 1. Calculate your Coast FIRE number 2. Save aggressively until you hit it 3. Let compound interest do the rest 4. Live your life with financial freedom
Use our Coast FIRE calculator to find your number and start planning your path to financial freedom today!
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