You're buying a $400,000 house with 20% down. Your loan amount: $320,000.
The bank offers two options at 6.5% interest:
- 30-year mortgage
- 15-year mortgage
Which do you pick?
Most people pick the 30-year because the monthly payment is lower.
But here's what that choice actually costs.
The Real Numbers
$320,000 loan at 6.5% APR:
| Loan Term | Monthly Payment | Total Paid | Total Interest | |-----------|----------------|------------|----------------| | 30-year | $2,024 | $729,640 | $409,640 | | 15-year | $2,787 | $501,660 | $181,660 |
The difference: $228,000 in interest.
Same house. Same interest rate. Just different terms.
By choosing 30 years instead of 15, you pay an extra $228,000 to the bank.
Why the 30-Year Costs So Much More
With a 30-year loan, you're paying interest on the full balance for longer.
Year 1, Month 1 on a 30-year loan:
- Payment: $2,024
- Interest: $1,733
- Principal: $291
You pay $2,024 and only $291 goes toward owning the house. The rest is bank profit.
Year 1, Month 1 on a 15-year loan:
- Payment: $2,787
- Interest: $1,733
- Principal: $1,054
Same interest charge. But $1,054 goes to principal instead of $291.
That's 3.6x more principal paydown from day one.
This compounds over time. The faster you pay down principal, the less future interest you owe.
The Monthly Payment Trade-Off
The 15-year payment is $763 more per month.
That's real money. On a $320,000 loan:
- 30-year: $2,024/month
- 15-year: $2,787/month
Is paying $763 more worth saving $228,000?
Math says yes. But it depends if you can afford it.
The question: Can your budget handle $2,787/month comfortably?
If yes → 15-year saves you massive money.
If no → 30-year keeps you from being house-poor.
When the 15-Year Makes Sense
Choose 15-year if:
✅ The payment is <28% of your gross income
✅ You have a stable income
✅ You have an emergency fund (6 months)
✅ You're maxing out retirement contributions
✅ You have no high-interest debt (>6%)
Example:
Household income: $120,000/year = $10,000/month gross
28% rule: $10,000 × 0.28 = $2,800 max housing payment
A $2,787 mortgage payment fits perfectly.
You can afford the 15-year and should take it.
When the 30-Year Makes Sense
Choose 30-year if:
✅ The 15-year payment is >28% of gross income
✅ Your income is variable/uncertain
✅ You have other financial priorities (kids' college, starting business)
✅ You're an investing opportunity optimizer
✅ You value cash flow flexibility
The flexibility argument:
With a 30-year loan, you can always pay extra toward principal (making it a pseudo 15-year).
But with a 15-year loan, you're locked into that $2,787 payment. If life happens, you can't reduce it.
Some people prefer the 30-year payment with the option to pay more, not the obligation.
The Wealth-Building Argument
Here's where it gets interesting.
Scenario: You can afford the 15-year payment ($2,787/month).
Option A: 15-year mortgage
- Pay $2,787/month
- Mortgage-free in 15 years
- Saved $228,000 in interest
Option B: 30-year mortgage + invest the difference
- Pay $2,024/month on mortgage
- Invest $763/month in index funds
- Assume 8% annual returns
After 15 years:
- Option A: Own home, $0 debt, $0 investments
- Option B: Owe $189,000 on mortgage, have $265,000 invested
Net worth difference: Option B wins by $76,000
($265,000 investments - $189,000 remaining mortgage = $76,000 ahead)
But here's the catch:
This assumes:
- You actually invest that $763 every month for 15 years
- Markets return 8% (not guaranteed)
- You don't panic sell during downturns
- Your mortgage rate is <8% (so investing beats it)
Most people don't have this discipline.
They spend the $763 instead of investing it. The 15-year mortgage forces savings.
The Break-Even Math
At what mortgage rate does the 15-year always win?
If your mortgage rate is >6-7% APR, paying it off beats investing.
Why? Historical stock market returns average ~10%, but after inflation (3%) and taxes (20%), you're at ~5.6% real returns.
If your mortgage costs 7%+ and you're only earning 5.6% investing, paying off the mortgage is the better investment.
At rates below 5%, investing might build more wealth.
At rates above 7%, paying off the mortgage wins.
At 5-7%, it's a toss-up based on your risk tolerance.
What If You Pick Wrong?
Picked 30-year and regret it?
You can:
- Refinance to a 15-year (if rates are good)
- Make extra principal payments manually
- Pay one extra payment per year (cuts 4-6 years off the loan)
Picked 15-year and struggling?
You can:
- Refinance to a 30-year (extends your payments, reduces monthly cost)
- But you lose the time you've already invested
Bottom line: It's easier to go from 30 to 15 than 15 to 30.
The Hidden Third Option
What if you pick a 20-year or 25-year term?
Many lenders offer these. They're the middle ground:
- Lower payment than 15-year
- Less total interest than 30-year
- Faster payoff than 30-year
Example: $320,000 at 6.5%
| Term | Monthly Payment | Total Interest | |------|----------------|----------------| | 30-year | $2,024 | $409,640 | | 20-year | $2,387 | $252,880 | | 15-year | $2,787 | $181,660 |
A 20-year saves you $156,760 vs the 30-year, but only costs $363/month more.
If the 15-year is too tight but the 30-year feels wasteful, ask about a 20-year.
The Decision Framework
Ask yourself:
- Can I comfortably afford the 15-year payment? (Is it <28% of gross income?)
- Do I have 6 months emergency fund saved?
- Am I maxing out my 401k match?
- Do I have high-interest debt (>6%)?
If all answers are YES → Choose 15-year
If any answer is NO → Choose 30-year
But don't just pay minimums on the 30-year. Pick a fixed amount above the minimum and stick to it.
The Final Word
The 15-year mortgage saves you $200,000+ in interest and gets you debt-free in half the time.
But it requires discipline, stable income, and higher monthly payments.
The 30-year mortgage gives you flexibility and lower payments, but costs you significantly more over time.
There's no universally right answer.
Financially optimal ≠ emotionally sustainable.
Pick the one you'll stick with for the full term.
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See Your Numbers
Use the Mortgage Calculator to:
- Compare exact payment amounts for 15 vs 30-year terms
- See total interest paid over the life of each loan
- Calculate how extra payments change your payoff timeline
- Find your monthly payment at different rates and terms
Run your real numbers before you decide.
Next: How Much House Can I Actually Afford? - The 28% rule explained with real income examples.