You are buying a $400,000 home. The lender gives you two options: a 30-year mortgage at 6.8% or a 15-year mortgage at 6.2%. The 15-year rate is lower — a full half point. You want to save on interest. But the monthly payment on the 15-year is much higher. You are not sure if you can afford it. You search for a comparison online, but every site pushes you to "talk to a lender" who will almost certainly recommend the 30-year because it is easier to qualify for.
Most online mortgage calculators are designed to keep you on the 30-year path. Lenders make more money from 30-year loans because you pay interest for twice as long. Bankrate, NerdWallet, and LendingTree all have 30-year as the default. Their calculators do not show you the brutal math of the 15-year unless you manually change the term. And even then, they make the 15-year look scary by highlighting the higher monthly payment without showing the massive interest savings.
The decision between a 30-year and a 15-year mortgage is not just about monthly cash flow. It is about your stage of life, your other financial goals, and your tolerance for risk. I am going to show you the real numbers for a $420,000 home (the 2026 median) with 20% down. Then you can decide which path makes sense for you.
Let me lay out the exact math. Home price: $420,000. Down payment: 20% ($84,000). Loan amount: $336,000. For a 30-year fixed at 6.8%, the monthly principal and interest payment is $2,191. Total interest paid over 30 years: $453,000. Total paid (principal + interest): $789,000. For a 15-year fixed at 6.2%, the monthly principal and interest payment is $2,869. That is $678 more per month. Total interest paid over 15 years: $180,000. Total paid: $516,000.
The difference in total interest is $273,000. That is real money. That is a year of salary for many people. If you can afford the extra $678 per month, the 15-year saves you nearly three-quarters of a million dollars over the life of the loan? Wait, $273,000, not $750,000. Still huge. But here is the catch. That $678 per month invested in the stock market at an average 7% return over 15 years would grow to about $210,000. So the opportunity cost is real. If you are a disciplined investor, you might come out ahead by taking the 30-year and investing the difference.
But most people do not invest the difference. They spend it. The 30-year gives you flexibility. If you lose your job or have an emergency, you can drop down to the lower $2,191 payment. With the 15-year, you are locked into $2,869. That extra $678 per month is a commitment. For a dual-income household with stable jobs, the 15-year might be worth it. For a single buyer or someone with variable income, the 30-year is safer.
Let me add one more scenario. What if you take the 30-year but make extra payments equal to the 15-year payment? You would pay $2,869 per month on the 30-year loan. That extra $678 goes straight to principal. You would pay off the 30-year loan in about 15.5 years — slightly longer than the 15-year term. Total interest paid would be about $190,000, which is $10,000 more than the 15-year loan at 6.2%. The difference is because the 15-year has a lower interest rate. So if you can qualify for the lower rate, the 15-year is mathematically better. But many lenders offer the same rate for both terms, in which case the math flips.
Here is how to run the numbers for your specific situation without giving up your email.
Bankrate's 30-year vs 15-year comparison page is designed to push you toward a lender. The page has a large banner: "See Today's Rates." When you click it, you enter your zip code, email, and phone number. That lead is sold to multiple lenders. Bankrate earns commission on any loan that closes. They do not care if you choose the 30-year or 15-year. They just want you to click.
NerdWallet's comparison tool is slightly better. They show real rate data from partner lenders. But to see the rates, you must provide your contact information. That information goes to the lenders listed. You will get calls from each of them. NerdWallet earns a fee per lead, typically $50 to $200.
The most misleading are the "calculator" sites that are actually lead generation companies. They have names like "MortgageCalculator.org" and "CalculateMyMortgage.com." These sites are owned by lending networks. Every input you type is tracked and saved. Even if you do not click "submit," they have your IP address and the numbers you entered. They can match that data to your identity through third-party data brokers.
Truly Free Mortgage Calculator does not track your inputs. There is no lead form. No "compare rates" button. No lender network. The only way I make money is from AdSense ads on the page. You can run as many comparisons as you want, and your phone will never ring. That is the difference between a tool and a trap.
No account. No email. Runs in your browser.
Run the comparison yourself. Enter your numbers. See the real dollar difference. Then decide what works for your budget and your sleep-at-night factor.
Figures on this page are for educational purposes only. Rates, tax rates, and insurance costs vary by lender, location, and borrower profile. Consult a licensed lender for loan-specific figures. Truly Free Mortgage Calculator does not collect personal data and does not connect users with lenders.
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