Coast FIRE with a Family: Planning for Kids, Mortgage, and College (2026)
Coast FIRE is not just for single people in their 20s. Families can reach it too - here is how to adjust the math for kids, a mortgage, and college savings.
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The Key Insight
Your Coast FIRE number is based on retirement expenses - not what you spend raising a family right now. Kids eventually leave. Mortgages get paid off. A family spending $100k/year today might only need $50-60k in retirement. That means your Coast FIRE target may be lower than you think.
Why Coast FIRE Works for Families
Most FIRE content is written by and for single people or DINKs (dual income, no kids). That leaves parents feeling like financial independence is out of reach. But Coast FIRE is arguably better suited for families than traditional FIRE.
Here is why:
1. Your target is lower than you think
Families have massive temporary expenses: diapers, childcare, kids' activities, bigger car, bigger house. These vanish by retirement. Your Coast FIRE number is based on post-kid retirement spending.
2. You do not need to save forever
Traditional FIRE asks parents to save 50%+ of income for 15-20 years while also paying for childcare and extracurriculars. Coast FIRE says: save hard for 5-10 years, then stop and redirect that money to family life.
3. Career flexibility when you need it most
After hitting Coast FIRE, one parent can go part-time, stay home, or take a less demanding job. This is often more valuable to families than full early retirement decades later.
Coast FIRE Numbers for Families
The math does not change for families - only the inputs. Your Coast FIRE number depends on your retirement expenses (not current family expenses), your age, and expected returns.
| Family Retirement Spending | FIRE Number | Coast FIRE at 30 | Coast FIRE at 35 |
|---|---|---|---|
| $40,000/year | $1,000,000 | $131,000 | $184,000 |
| $50,000/year | $1,250,000 | $163,000 | $229,000 |
| $60,000/year | $1,500,000 | $197,000 | $276,000 |
| $80,000/year | $2,000,000 | $263,000 | $368,000 |
Assumes 7% real returns, retirement at 60. Retirement spending excludes mortgage and child-related expenses.
Notice: a family spending $100k today but only $50k in retirement needs a Coast FIRE number of just $163k at age 30. That is achievable in 5-7 years even on a moderate family income.
The Mortgage Question
Your mortgage is probably your family's biggest expense. How you handle it significantly changes your Coast FIRE math.
Scenario A: Mortgage paid off before retirement
If your mortgage will be paid off by 55-60, exclude housing costs from retirement expenses. A family paying $2,000/month on a mortgage eliminates $24,000/year from their retirement budget. This can cut your FIRE number by $600,000 and your Coast FIRE number by $79,000-$110,000.
Scenario B: Mortgage extends into retirement
If you bought your home late or refinanced to a longer term, include mortgage payments in retirement expenses. This raises your number but is realistic. Do not pretend the payment does not exist.
MORTGAGE IMPACT EXAMPLE
Family, age 35, current spending $100k/year
With mortgage in retirement:
$276,000 Coast FIRE
($60k retirement spend)
Without mortgage in retirement:
$184,000 Coast FIRE
($40k retirement spend)
The takeaway: paying off your mortgage before retirement can reduce your Coast FIRE number by 33%. This does not mean you should rush to pay it off early - invest first if your mortgage rate is below your expected investment return.
Kids and College Savings
This is where most parents get stuck. They feel they cannot save for retirement and college and afford daily family life. Coast FIRE offers a solution: sequence your priorities.
The recommended order
| Priority | Action | Why |
|---|---|---|
| 1st | 401(k) match | Free money. Always take the match. |
| 2nd | Emergency fund (3-6 months) | Protects family from crisis. |
| 3rd | Max retirement accounts | Reaches Coast FIRE. No financial aid for retirement. |
| 4th | 529 college savings | Financial aid, loans, and scholarships exist for college. |
The College vs. Retirement Math
A dollar saved for retirement at 30 becomes roughly $7.60 by 60 (at 7% returns). A dollar saved for a 5-year-old's college in a 529 becomes about $2.40 by age 18. Retirement savings compound longer and have no alternative funding source.
Once you hit Coast FIRE, the money you were putting toward retirement ($20-40k/year) can flow directly into 529 plans. You will likely have 10+ years of Coast FIRE mode to fund college.
Find your family's Coast FIRE number
Enter your retirement expenses (not your current family budget) to see how close you are.
Calculate NowDual Income Strategies
Dual-income families have the biggest advantage in the Coast FIRE game. Here are three proven strategies:
Strategy 1: Live on one income, invest the other
If Partner A earns $70k and Partner B earns $60k, live on the $70k and invest most of the $60k. At $40-50k/year in investments, you could hit Coast FIRE in 4-6 years. This is the fastest path but requires discipline and relatively low housing costs.
Strategy 2: Max both 401(k)s first
Two 401(k)s at $23,500 each (2026 limit) = $47,000/year in tax-advantaged retirement savings. Combined with employer matches (typically 3-6%), a couple could invest $55-60k/year. At 7% returns, that reaches $200k in under 4 years. Coast FIRE before the kids start kindergarten.
Strategy 3: Sprint then one stays home
Both partners work and save aggressively for 5-7 years. Once you hit Coast FIRE, one parent quits or goes part-time. You have already secured retirement - the remaining income only needs to cover current living expenses. This is the most popular family Coast FIRE strategy.
Example: The Thompson Family
Dan (29) and Maria (28) both earn $75k. They max out both 401(k)s ($47k/year) and invest another $15k in a brokerage account. After 4 years they have ~$290k invested. Their Coast FIRE number is $197k (targeting $60k/year retirement at 60). They passed Coast FIRE at year 3. Maria now works 3 days/week as a consultant. They lost $30k in income but gained two extra days per week with their toddler.
Single Income Families
Coast FIRE is harder on one income but far from impossible. The key is adjusting expectations and being strategic.
| Family Income | Savings Rate | Annual Investment | Years to $200k |
|---|---|---|---|
| $60,000 | 15% | $9,000 | 14 years |
| $80,000 | 20% | $16,000 | 9 years |
| $100,000 | 25% | $25,000 | 6 years |
| $120,000 | 30% | $36,000 | 5 years |
Assumes 7% returns, starting from $0, Coast FIRE target of $200k.
Even at $60k with a modest 15% savings rate, a single-income family can hit Coast FIRE in 14 years. That means starting at 28, you are Coast FIRE by 42 - with potentially 18 years of reduced savings pressure ahead.
Family Coast FIRE Action Plan
Step 1: Calculate your retirement expenses (not current)
Take your current spending. Remove: childcare, kids' activities, college savings, mortgage (if paid off by then), larger car payment. Add: healthcare (pre-Medicare), travel, hobbies. Most families find retirement expenses are 40-60% of their current budget.
Step 2: Find your Coast FIRE number
Use the Coast FIRE Calculator with your retirement expenses. This is your target. For most families, it is between $150k-$350k.
Step 3: Max tax-advantaged accounts first
401(k)s, IRAs, and HSAs. If you and your partner both have 401(k)s, maxing both puts you at $47k/year in retirement savings alone. Most families hit Coast FIRE from tax-advantaged accounts without needing a brokerage account.
Step 4: Hit the number, then redirect
Once you reach Coast FIRE, stop contributing to retirement and redirect that money toward: 529 college savings, a mortgage payoff fund, family experiences, or a career transition buffer fund.
Calculate your family's Coast FIRE number
Use retirement expenses (not your current family budget) for an accurate result.
Coast FIRE CalculatorFrequently Asked Questions
Can you reach Coast FIRE with kids?
Yes. Kids increase current expenses but do not change the core Coast FIRE math. Your Coast FIRE number is based on retirement expenses (after kids leave home), not current family spending. The challenge is maintaining savings during high-expense years, not hitting a higher target.
Does a mortgage affect your Coast FIRE number?
Only if you plan to carry the mortgage into retirement. Most families will have their mortgage paid off by traditional retirement age. If your mortgage is paid off by 60, exclude it from your retirement expense estimate. This significantly lowers your Coast FIRE number.
Should we save for college or Coast FIRE first?
Prioritize Coast FIRE contributions to retirement accounts first. Retirement has no financial aid; college does. You can borrow for college but not for retirement. Once you hit Coast FIRE, redirect retirement contributions toward a 529 plan.
How do dual incomes affect Coast FIRE?
Dual incomes accelerate Coast FIRE dramatically. If one partner earns enough to cover family expenses, the other can invest 100% of their income. Many dual-income families hit Coast FIRE in 5-7 years using this strategy.
What happens to our Coast FIRE plan if one parent stays home?
Going from dual to single income slows progress toward Coast FIRE but does not reset it. Money already invested keeps compounding. The key decision is whether to hit Coast FIRE before or after the income drop. If possible, front-load savings during dual-income years.
Is Coast FIRE realistic on a single family income?
Yes, though it takes longer. A family earning $90k with a 20% savings rate ($18k/year) can reach Coast FIRE in roughly 8-12 years depending on age. The advantage is that family expenses drop significantly once kids are independent, making a Coast FIRE lifestyle very achievable.