30-Year vs 15-Year Mortgage: Which Is Right for You?

The choice between a 30-year and 15-year mortgage is one of the most consequential financial decisions homebuyers make. The right answer depends on your cash flow, financial goals, risk tolerance, and what else you’d do with the payment difference.

The Core Trade-Off

Factor	30-Year Mortgage	15-Year Mortgage
Monthly payment	Lower	Higher
Total interest paid	Much higher	Much lower
Interest rate	Higher (typically)	Lower (typically)
Equity building speed	Slow early on	Fast
Cash flow flexibility	More	Less
Time to payoff	30 years	15 years
Risk	Lower monthly obligation	Higher monthly obligation

Side-by-Side Payment Comparison

$400,000 Purchase Price, $80,000 Down ($320,000 Loan)

	30-Year at 6.5%	15-Year at 5.75%
Monthly principal + interest	$2,023	$2,658
Monthly difference	—	+$635
Total payments	$728,280	$478,440
Total interest paid	$408,280	$158,440
Interest savings (15-year)	—	$249,840

That $249,840 in interest savings is the headline. But the monthly difference of $635 is real money that could be invested or held as emergency reserve.

$600,000 Loan Comparison

	30-Year at 6.5%	15-Year at 5.75%
Monthly payment (P&I)	$3,792	$4,983
Monthly difference	—	+$1,191
Total interest paid	$765,491	$296,905
Interest savings	—	$468,586

At larger loan amounts, the interest savings become massive — but so does the payment increase.

The Investment Alternative Argument

The case for the 30-year mortgage often rests on one key insight: the $635/month payment difference could be invested.

Scenario: $320,000 loan, investing the $635/month difference

If you take the 30-year and invest $635/month for 15 years at an average 7% annual return:

• Total invested: $635 × 180 = $114,300
• Value after 15 years: ~$204,000
• Meanwhile, you still owe ~$218,000 on the 30-year mortgage

The investment grows to $204K — which doesn’t yet offset the remaining mortgage balance. But at 15 years, you’re still 15 years away from payoff, and the investments continue compounding.

Key assumption: This only works if you actually invest the difference consistently. Many people spend the extra cash flow rather than investing it.

Use the compound interest calculator to model how $635/month invested grows at different return assumptions.

When the 30-Year Makes More Sense

You should lean toward 30-year if:

1. Your emergency fund isn’t solid: The lower required payment preserves cash flow if you lose your job or face unexpected expenses.

2. You’re a disciplined investor: If you will invest the payment difference at returns exceeding your mortgage rate (6.5%), you may build more wealth.

3. Other high-interest debt exists: Paying off credit cards (20%+ APR) or student loans (6–8%) before accelerating mortgage payoff makes mathematical sense.

4. Job income isn’t stable: Freelancers, commission-based workers, and business owners benefit from lower required monthly obligations.

5. You plan to move within 10 years: You’ll likely refinance or sell before the 15-year’s extra interest savings fully materialize.

When the 15-Year Makes More Sense

You should lean toward 15-year if:

1. You want guaranteed payoff: The 15-year forces accelerated equity building with no discipline required.

2. You’re approaching retirement: Eliminating the mortgage before retiring is a clear financial goal. A 45-year-old taking a 15-year mortgage is mortgage-free at 60.

3. You don’t trust yourself to invest the difference: Behavioral finance is real. Forced savings via mortgage paydown is better than optional investing that doesn’t happen.

4. You’re risk-averse: The guaranteed 5.75% “return” (interest savings) feels better than volatile equity markets.

5. You can comfortably afford the payment: If the higher payment doesn’t strain your budget (mortgage payment under 28% of gross income), the math and peace of mind favor the 15-year.

The 30-Year with Extra Payments Strategy

A middle path: take the 30-year for payment flexibility, then make extra principal payments when you can.

Extra Payment Strategy	Years to Payoff	Interest Savings
No extra payments	30 years	Baseline
$200/month extra	~25 years	~$80,000
$500/month extra	~21 years	~$143,000
One extra payment/year	~24 years	~$60,000
15-year payment amount	15 years	~$250,000

This approach gives you the 30-year’s lower required payment for safety, while capturing some of the 15-year’s interest savings when your budget allows.

Break-Even Analysis: When Do the Interest Savings Pay for Themselves?

The 15-year’s higher payment accumulates meaningful interest savings only over time. Here’s how interest savings accumulate on the $320,000 example:

After Year	Cumulative Interest Savings
Year 5	~$40,000
Year 10	~$95,000
Year 15	~$250,000

If you sell or refinance before year 10, the interest savings are real but the payment premium was also real — the net benefit is smaller than the headline number suggests.

For a personalized mortgage comparison with your loan amount, rates, and location-specific taxes and insurance, use the paycheck calculator to understand how housing costs fit into your overall budget.