How to Use This Mortgage Comparison Calculator
Enter your inputs for Option A and Option B — home price, down payment, interest rate, loan term, property tax, insurance, and HOA fees. The calculator instantly computes each scenario's monthly payment and lifetime cost, then the comparison summary shows you the exact dollar difference and which option wins.
Common use cases: comparing two lenders' rate quotes, seeing whether to put 10% or 20% down, deciding between a 15-year and 30-year loan, or evaluating a buydown point offer.
What the Numbers Mean
- Monthly Payment — principal + interest + estimated property tax + homeowner's insurance + HOA. This is your true monthly housing cost.
- Total Interest Paid — the cumulative interest you pay over the full loan term. This is where loan comparisons diverge dramatically.
- Total Cost — total interest + principal repaid + down payment. The true price you pay for the home.
15-Year vs 30-Year: The Biggest Trade-Off
The most common comparison is 15-year vs 30-year. On a $400,000 loan at 6.5%, a 30-year mortgage has a P&I payment of about $2,528/month but costs $510,000 in interest over 30 years. The same loan at 15 years costs $3,484/month — $956 more — but total interest drops to just $227,000, saving over $280,000. Whether that trade-off makes sense depends on your cash flow and how long you plan to stay in the home.
Frequently Asked Questions
How do I compare two mortgage rates?
Enter each lender's rate into Option A and B above with identical loan amounts. The comparison summary will show the monthly payment difference and total interest savings over the life of the loan.
Is a lower interest rate always better?
Usually, but factor in origination fees and points. A 0.25% rate reduction that costs $4,000 in points takes about 3 years to break even at typical savings. If you plan to move sooner, the higher rate may actually cost less.
What's the difference between a 15-year and 30-year mortgage?
A 15-year mortgage pays off faster and saves 50–60% of the interest, but monthly payments are 30–40% higher. A 30-year is more affordable monthly but costs dramatically more over time. Use this tool to see the exact numbers for your loan amount.
How much does a 0.5% rate difference affect my mortgage?
On a $400,000 30-year loan, a 0.5% difference (6.5% vs 7.0%) means about $120/month more and roughly $43,000 more in total interest. On a 15-year loan the monthly difference is larger but the total interest difference is smaller.