Mortgage Comparison Calculator

A 30-year mortgage spreads payments over 360 months, giving you a lower monthly payment but charging significantly more total interest over the life of the loan. A 15-year mortgage has higher monthly payments but a shorter repayment window and a lower interest rate (because lenders face less default risk), so the total interest paid is usually far less. The mortgage comparison calculator lets you enter both scenarios side by side to see the exact monthly and lifetime cost differences for your specific loan amount and rates.

Mortgage points (also called discount points) are upfront fees paid to the lender at closing in exchange for a lower interest rate. One point equals 1% of the loan amount. Whether points are worth paying depends on the break-even period: divide the upfront cost by the monthly payment savings. If you plan to stay in the home or keep the mortgage longer than the break-even month, buying points saves money. This calculator computes the break-even month automatically when you enter upfront fees for one scenario and a lower rate for the other.

Neither answer is universally true. A lower rate generally means less interest, but a shorter-term loan (which often has a lower rate) requires higher monthly payments even though the total interest is much less. The most meaningful comparison is total cost — monthly payment times the number of months plus upfront fees and down payment. Use this calculator to compare total cost rather than just monthly payment.

The standard formula for a fixed-rate, fully-amortizing mortgage is M = P × r × (1 + r)^n ÷ ((1 + r)^n − 1), where P is the loan principal (home price minus down payment), r is the monthly interest rate (annual rate divided by 12), and n is the total number of monthly payments (term in years times 12). Each payment covers that month’s interest on the remaining balance, with the rest reducing the principal.

The break-even month is when your cumulative monthly payment savings from the lower-rate (higher-fee) loan equal the extra upfront cost you paid. Before the break-even month you have spent more in fees than you have saved in payments; after it, the lower-rate loan is ahead. This is only calculated when one loan has higher fees and lower monthly payments than the other. If you refinance or sell before the break-even, the higher-fee option costs you more overall.

Yes. Closing costs (origination fees, appraisal, title insurance, points) can range from 2% to 5% of the loan amount and directly affect total cost. A loan with a lower rate but high closing costs may not save money compared to a no-closing-cost option, depending on how long you keep the mortgage. Enter the upfront fees for each scenario in this calculator to get an accurate total-cost comparison and break-even month.

On a 30-year mortgage the balance amortizes slowly in the early years — most of each payment goes to interest, not principal. Over 360 payments the interest compounds on a persistently high balance. A 15-year mortgage makes the same amortization math work in half the time, so the balance shrinks much faster, each period’s interest charge is applied to a smaller outstanding balance, and the total interest compounds far fewer times. For a $320,000 loan at 6.5% vs 5.75%, the 30-year option can accrue roughly $250,000 more in interest than the 15-year, as shown in Example 1 of this calculator.

No. This calculator computes the principal-and-interest (P&I) portion of your payment only. Property taxes, homeowners insurance, and private mortgage insurance (PMI — typically required when the down payment is less than 20%) are excluded. Your actual monthly outlay will be higher once these are added. Lenders call the full payment PITI (principal, interest, taxes, insurance). Use the P&I figures here for a clean comparison between loan structures, and add your PITI estimates separately for budgeting.

The calculator uses the same home price and down payment for both scenarios, so both loans share the same principal. This is the correct way to compare mortgage offers on the same property. If you want to compare two properties at different price points (and therefore different loan amounts), you would need to run two separate calculations. The key insight is that changing the rate or term alone — on the same principal — isolates the pure cost difference between loan structures.

Mortgage rates vary with monetary policy, lender competition, your credit score, loan-to-value ratio, and loan type. The Federal Reserve H.15 release publishes benchmark conventional mortgage rates. Even a 0.5% rate difference on a $300,000 loan can change your total interest by $30,000 or more over 30 years. The best way to understand a rate’s impact is to plug both offers into a side-by-side comparison like this calculator and look at the total-cost difference.