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15-Year vs. 30-Year Mortgage Calculator

Compare 15-year and 30-year fixed mortgages side-by-side. Calculate exact monthly payment differences, lifetime interest saved, and investment opportunity costs to find the smartest mortgage strategy for your goals.

Quick Scenarios
Total negotiated purchase price of the property.
Upfront cash down payment (20% down avoids private mortgage insurance).
Current market rate for a 15-year fixed loan (historically 0.5% to 1.0% lower than 30-year).
Current market rate for a 30-year fixed loan.
Local annual property tax divided into 12 escrow payments.
Yearly hazard/homeowners insurance premium.
Historical annualized nominal stock market index return (long-term average is ~8-10%).
Analyze your net wealth at the 15-year mark when the 15-year loan is fully paid off.
Expected annual increase in property value (national historical average is ~3-4%).

Guaranteed Debt Payoff Wins

The 15-year mortgage saves $265,778.95 in guaranteed interest. However, choosing the 30-year mortgage and consistently investing the $598.96/month difference at 8% annual return can build an investment portfolio of $208,644.81 in 15 years — producing $25,900.53 less overall wealth.

Total Interest Saved (15-Yr) $265,778.95
15-Year Monthly Payment $3,174.48
30-Year Monthly Payment $2,575.51
Monthly Payment Difference + $598.96 / mo
Invested Difference at 15 Yrs $208,644.81
Net Wealth with 15-Yr Loan $670,139.53
Net Wealth with 30-Yr + Investing $644,239.00
Principal Loan Balance $320,000.00

15-Year vs. 30-Year Mortgage: The Comprehensive Decision Guide

Deciding between a 15-year and 30-year mortgage is not just about monthly payments — it is a foundational strategic choice between guaranteed debt elimination and stock market wealth building.

Guaranteed Return vs. Market Opportunity Cost

Paying off a 15-year mortgage at 5.85% is equivalent to earning a guaranteed, risk-free 5.85% return on your money. Choosing a 30-year loan and investing the monthly cashflow difference in diversified index funds (averaging 7% to 10% historically) has higher expected long-term wealth, but comes with market volatility.

Cash Flow Flexibility: The Sleep-at-Night Factor

A 30-year mortgage provides a lower mandatory monthly payment. If you face unexpected job loss or medical expenses, your required commitment is lower. If you have extra cash in good months, you can always prepay principal at your own pace.

How to Use the 15-Year vs. 30-Year Mortgage Calculator

  1. 1
    Enter the property purchase price and cash down payment (20% down avoids PMI).
  2. 2
    Input the current 15-year and 30-year fixed interest rates quoted by your lender.
  3. 3
    Set your property tax, insurance, and expected index fund return in Advanced Options.
  4. 4
    Compare total interest saved, monthly payment differences, and the multi-year investment opportunity cost.

Frequently Asked Questions

Is a 15-year mortgage always better than a 30-year mortgage?

No. While a 15-year mortgage saves massive interest, the higher mandatory payment restricts cash flow. If investing the monthly difference in tax-advantaged retirement accounts (401k/IRA), a 30-year mortgage can actually yield a higher overall net worth.

Can I pay off a 30-year mortgage in 15 years?

Yes! Standard mortgages in the US have no prepayment penalties. You can take a 30-year loan for safety and make extra principal payments each month to retire the loan in 15 years.

How much lower is the interest rate on a 15-year mortgage?

Typically, 15-year fixed mortgage rates are 0.50% to 1.00% lower than 30-year fixed rates because lenders take on less duration risk.

What happens to my payment when the 15-year loan is paid off?

Your principal and interest payment drops to $0. You only pay property taxes, hazard insurance, and maintenance costs going forward.