15 vs 30 Year Mortgage Calculator

How this 15 vs 30 year mortgage calculator works

This calculator compares a shorter-term mortgage (typically 15 years) with a longer-term mortgage (typically 30 years) using the same loan amount but different interest rates and terms. It shows:

• Monthly principal & interest payment for each term
• Total interest paid over the life of each loan
• Estimated total monthly housing cost including taxes, insurance, and HOA dues
• Optional: the effect of investing the payment difference if you choose the 30-year loan

Mortgage payment formula

For a fixed-rate mortgage, the monthly principal and interest payment is calculated using the standard amortization formula:

Total interest paid over the life of the loan is:

15-year vs 30-year mortgage: key trade-offs

15-year mortgage: pros and cons

• Pros:
  • Much less total interest paid
  • Faster path to being mortgage-free
  • Typically lower interest rate than a 30-year loan
  • Builds home equity more quickly
• Cons:
  • Higher required monthly payment
  • Less cash flow flexibility if your income drops or expenses rise
  • May reduce your ability to save for retirement or other goals

30-year mortgage: pros and cons

• Pros:
  • Lower required monthly payment
  • More room in your budget for savings, emergencies, and other goals
  • Option to make extra principal payments when you can
• Cons:
  • Higher interest rate than a 15-year loan in most markets
  • Much more total interest over the life of the loan
  • Slower equity build-up

When a 15-year mortgage may make sense

Choosing a 15-year mortgage can be a good fit if:

• Your income is stable and comfortably supports the higher payment.
• You already have a solid emergency fund (e.g., 3–6+ months of expenses).
• You are on track with retirement savings and other long-term goals.
• You value being debt-free sooner more than maximizing investment flexibility.

When a 30-year mortgage may be better

A 30-year mortgage can be more appropriate if:

• You need a lower required payment to qualify or to feel comfortable.
• You have variable income or expect life changes (kids, career shift, etc.).
• You want to prioritize retirement savings, debt payoff, or building an emergency fund.
• You plan to invest the payment difference and are comfortable with market risk.

Strategy: 30-year mortgage, 15-year payments

A common compromise is to take a 30-year mortgage for flexibility, but voluntarily pay extra principal each month so that your effective payoff schedule is close to 15 years.

• Upside: You can drop back to the lower required payment in tight months.
• Downside: The interest rate is usually higher than a true 15-year loan, so even with extra payments you may pay more interest overall.

You can approximate this strategy in the calculator by:

1. Entering the 30-year rate and term.
2. Using the 15-year payment as your target extra payment on the 30-year loan.
3. Comparing total interest and cash flow flexibility.

Limitations and assumptions

• The calculator assumes fixed interest rates and level payments for the full term.
• It does not model mortgage insurance (PMI), closing costs, or tax deductions.
• Investment returns are hypothetical and not guaranteed; actual results will vary.
• Property taxes, insurance, and HOA dues are treated as constant monthly amounts.

Use these numbers as a starting point for conversations with a lender or financial planner, not as a final decision on their own.