15-Year vs 30-Year Mortgage Calculator 2026

A 15-year mortgage usually saves you 60-70% of the total interest compared to a 30-year — but at the cost of a 40-50% higher monthly payment. The right choice depends on how much margin you have in your budget, your job stability, and whether you have higher-return uses for the cash. This calculator runs both terms side-by-side so you can see the exact monthly trade and lifetime interest savings.

The math: why 15-year saves so much

A 30-year mortgage at 6.5% has a curious property: in year 1, only 22% of each monthly payment goes to principal — the other 78% is interest. Over 30 years, you pay roughly $382,000 in interest on a $320,000 loan ($702K total payments).

A 15-year mortgage at the same loan amount but typical lower rate (5.75%) has 41% of each payment going to principal in year 1. Over 15 years, total interest is only ~$159,000 ($479K total payments).

Difference: $223,000 less interest paid. That’s real money.

Why 15-year rates are lower

15-year mortgages typically carry rates 0.5-0.75% lower than 30-year. Two reasons:

1. Lower lender risk: shorter repayment = less time exposed to default or interest rate changes
2. Faster principal payoff: more principal early means lower remaining balance at risk

In 2026, typical spread: 30-year at 6.5%, 15-year at 5.75%. The spread widens in volatile rate environments.

When 15-year wins

• You can comfortably afford the higher payment without sacrificing emergency savings, retirement contributions, or other financial goals
• You’re 40+ years old and want to be mortgage-free by retirement
• You don’t have high-interest debt to pay off first (credit cards, personal loans)
• You’re already maxing tax-advantaged accounts (401k match, Roth IRA, HSA)
• You want forced savings through faster equity build-up

When 30-year wins

• The extra cash flow is more valuable invested elsewhere (especially if your alternative is stocks at expected 7-10% returns)
• You need flexibility for variable income, business ownership, or potential career changes
• You have high-interest debt that should be paid off first
• You’re not maxing retirement accounts
• You plan to move within 5-7 years (the 15-year’s interest savings don’t fully kick in until later)

The investment-arbitrage argument

The counterargument to 15-year: “I can get a 30-year at 6.5%, pay the minimum, and invest the difference at 8% in stocks. Over 15 years, I’d come out ahead.”

This is mathematically defensible IF:

• You actually invest the difference (most people don’t — they spend it)
• Your investment return outperforms 6.5% after tax over a long horizon
• You can tolerate stock market volatility

For most disciplined investors, the 30-year + invest strategy generates higher net worth over 30 years. For most ordinary households, the forced-saving 15-year mortgage builds more wealth because it removes the temptation to spend.

The hybrid strategy: 30-year + extra principal

Take the 30-year mortgage but pay it like a 15-year by adding extra principal each month. Benefits:

• Lower required minimum payment (flexibility in lean months)
• Same payoff timeline as 15-year if you stay disciplined
• No commitment risk — you can adjust extra principal up or down based on circumstances

Drawbacks:

• Higher interest rate than a true 15-year (~0.5-0.75%)
• Requires discipline to actually make extra principal payments

Use our mortgage payoff calculator to model this scenario.

Practical recommendation framework

Run the math, then ask yourself three questions:

1. Can I afford the 15-year payment comfortably? If it’s more than 25% of your gross income, the answer is probably no.
2. What would I do with the extra cash flow? If “invest in stocks consistently,” 30-year + invest may be better. If “spend on lifestyle,” 15-year forces better outcomes.
3. How stable is my income? Stable W-2 employee, single income: either works. Variable income, business owner, single income with kids: 30-year for flexibility.

Related calculators

• Mortgage Payoff Calculator — pay off a 30-year on a 15-year schedule with extra principal
• Refinance Break-Even Calculator — should you refi from 30-year to 15-year?
• Home Affordability Calculator — can you afford the 15-year payment?
• All Calculators

Estimates only. Real mortgage rates depend on credit, down payment, loan program. Not financial advice.