15 vs 30 Year Mortgage Calculator

Compare 15-year and 30-year mortgage terms side by side. See how much interest you save with a shorter term, the monthly payment trade-off, and what investing the difference could earn you over time.

Or enter as percentage below
Overrides $ amount above
Expected annual return if investing the difference
Total Interest Saved With 15-Year
—
15-Year Mortgage
Monthly Payment—
Total Interest—
Total Cost—
Rate—
30-Year Mortgage
Monthly Payment—
Total Interest—
Total Cost—
Rate—
Monthly Difference
—
30yr Investment Growth
—
Net Advantage
—
Ad Space

How 15 vs 30 Year Mortgage Comparison Works

This calculator compares two of the most common mortgage terms side by side using standard amortization formulas. Based on Freddie Mac Primary Mortgage Market Survey (PMMS) data, 15-year rates typically run 0.50-0.75% below 30-year rates. The shorter term means higher monthly payments but dramatically less total interest paid over the life of the loan — often saving homeowners $100,000 or more on a typical $300,000 mortgage. Last updated: 2026.

The Investment Opportunity Cost Argument

Financial advisors often debate whether the monthly savings from a 30-year mortgage should be invested instead. If you take the 30-year loan and invest the payment difference monthly at an assumed market return (historically 8-10% for the S&P 500), the investment portfolio could potentially exceed the interest savings of the 15-year option. However, this strategy requires discipline to actually invest the difference every month and assumes consistent market returns, which are never guaranteed.

When to Choose 15-Year vs 30-Year

Choose a 15-year mortgage if you can comfortably afford payments without exceeding 25% of gross income, want to build equity rapidly, or plan to retire the mortgage before retirement. Choose a 30-year mortgage if you need lower payments for cash flow flexibility, prefer to maximize tax-advantaged investments (401k, IRA) first, or want a larger emergency fund. Many borrowers compromise by taking a 30-year mortgage but making extra principal payments when possible.

Rate Spread and Market Conditions

The rate difference between 15 and 30 year mortgages fluctuates with Federal Reserve policy and bond market conditions. When the yield curve is steep, the spread widens (favoring 15-year even more). When the curve is flat or inverted, the spread narrows, making 30-year loans relatively more attractive. Check current rates from multiple lenders — the spread between lenders on the same product can exceed the spread between terms at one lender.