How it works
Both mortgages are computed with their respective rates and terms. The difference in total interest shows the true cost of the longer term. Every loan has four components: principal, interest rate, term, and fees. Understanding how these interact helps you compare offers apples to apples. A lower interest rate with high fees may cost more than a slightly higher rate with no fees. Always calculate the total cost of the loan — the sum of all payments over the full term — rather than focusing solely on the monthly payment. Every loan has four components: principal, interest rate, term, and fees. Understanding how these interact helps you compare offers apples to apples. A lower interest rate with high fees may cost more than a slightly higher rate with no fees. Always calculate the total cost of the loan — the sum of all payments over the full term — rather than focusing solely on the monthly payment.
Tips
- Start with the default values to see a baseline result, then change one input at a time to understand which factor matters most for your outcome.
- Replace every default with your actual number — estimates and rules of thumb produce estimates, not answers. Pull your real figures from pay stubs, statements, or account dashboards.
- Compare the total cost of borrowing, not just the monthly payment. A lower monthly payment often means paying thousands more in interest over the life of the loan.
Frequently asked questions
- How much more is a 15-year vs 30-year payment?
- A 15-year payment is typically 35-40% higher, but you save 40-50% in total interest. For a $300K loan, the difference can be over $150,000 in interest savings.
- What does the 15-year vs 30-year mortgage calculator calculate?
- It takes loan amount, 15-year rate %, 30-year rate % as inputs and computes 15-year monthly payment, 30-year monthly payment, 15-year total interest, 30-year total interest, interest savings (15yr). The primary output is 15-year total interest. Compare total interest costs, monthly payments, and wealth building between 15-year and 30-year mortgage terms.
- How accurate are the calculator results?
- The math is exact — the same formulas a financial professional would use by hand. The precision of the output depends entirely on how realistic your inputs are. Use your actual numbers rather than estimates when possible. The defaults are reasonable starting points, but your real income, rates, and timeline will produce a different result.