15-Year vs. 30-Year Mortgage Calculator

Trying to decide between a 15-year and a 30-year mortgage? The right term can save you tens of thousands of dollars in interest — or free up hundreds of dollars in your monthly budget, depending on what you value more. Use the calculator below to run each term with your real numbers, then compare the monthly payment and total interest side by side.

15-Year vs. 30-Year Mortgages: What's the Real Difference?

Both loans finance the same home with the same fixed interest rate structure — the only variable that changes is how many years you have to repay the balance. A shorter term means every payment is larger, but a much bigger share of it goes toward principal instead of interest, so the loan balance shrinks faster and the lender earns interest for far fewer years.

A 30-year mortgage stretches the same principal across twice as many payments. Each individual payment is smaller and easier to fit into a monthly budget, but because interest accrues on a larger remaining balance for a much longer stretch of time, the total interest paid over the life of the loan is dramatically higher — often more than double what the same loan would cost on a 15-year term, even at an identical rate.

Lenders also typically price 15-year mortgages at a lower interest rate than 30-year mortgages, since a shorter loan is less risky to the lender. That lower rate compounds with the shorter term to widen the total-interest gap even further.

Key Differences Between 15-Year and 30-Year Terms

• Monthly Payment: A 15-year term typically produces a monthly principal-and-interest payment 40-50% higher than the equivalent 30-year loan on the same balance and rate.
• Total Interest Paid: The 30-year term almost always costs significantly more in total interest — frequently two to three times as much as the 15-year term.
• Interest Rate: 15-year mortgages are usually priced at a somewhat lower rate than 30-year mortgages from the same lender on the same day.
• Equity Growth: Because more of each payment goes to principal, a 15-year mortgage builds home equity much faster in the early years.
• Budget Flexibility: The lower payment on a 30-year mortgage leaves more monthly cash flow for other goals — retirement contributions, an emergency fund, or simply breathing room.
• Qualifying Amount: Because the required payment is lower, buyers often qualify for a larger loan amount on a 30-year term than a 15-year term at the same income and debt levels.

How to Use This Calculator to Compare Both Terms

1. Enter the Loan Amount, Rate, and a 30-Year Term First

Input your loan amount, an estimated interest rate, and set the loan term field to 30. Note the monthly payment and total interest figures shown in the results panel.

2. Re-Run the Numbers with a 15-Year Term

Keep the loan amount the same, adjust the interest rate down slightly if your lender quotes a lower rate for 15-year loans, and change the loan term to 15. Compare the new monthly payment and total interest against what you noted in step 1.

3. Weigh the Monthly Payment Difference Against the Interest Savings

Subtract the 15-year monthly payment from the 30-year monthly payment — that's what a shorter term costs you every month. Then subtract the 15-year total interest from the 30-year total interest — that's what the longer term costs you over the life of the loan. Compare that monthly cost against your budget and financial goals.

4. Factor in Taxes, Insurance, and PMI

This calculator also factors in monthly property taxes, home insurance, and PMI, which don't change between the two scenarios — so the comparison above isolates exactly what term length changes, without those fixed costs distorting the picture.

Which Term Should You Choose?

A 15-year mortgage makes the most sense if you can comfortably afford the higher payment, want to own your home outright as fast as possible, and want to minimize the total interest paid over the life of the loan. It's a strong fit for buyers refinancing later in a mortgage's life, or anyone prioritizing being debt-free before retirement.

A 30-year mortgage makes more sense if you want maximum monthly flexibility, plan to invest the payment difference elsewhere (historically, long-run stock market returns have sometimes outpaced mortgage interest rates, though this isn't guaranteed), or need the lower required payment to qualify for the home you want. Many 30-year borrowers also make extra principal payments when cash flow allows, capturing some of the interest savings of a 15-year loan without locking themselves into the higher required payment every month.

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Tips for Choosing Between the Two Terms

1. Ask for Both Rate Quotes: Always ask your lender for the actual 15-year and 30-year rates you qualify for — the rate gap varies by lender and by market conditions.
2. Stress-Test the Higher Payment: Before committing to a 15-year term, model a temporary income disruption to make sure the higher required payment stays affordable.
3. Consider a Hybrid Approach: Take a 30-year mortgage for payment flexibility, but voluntarily pay extra principal each month calibrated to pay it off on roughly a 15-year schedule — you keep the lower required payment as a safety net.
4. Recheck After Refinancing: If you refinance a 30-year loan a few years in, run both term options again — your remaining balance and current rates may make a 15-year refinance more attainable than it was originally.

Common Mistakes to Avoid

• Comparing Payments Without Comparing Total Interest: Looking only at the monthly payment hides the very large total-interest difference between the two terms.
• Ignoring the Rate Difference: Using the same interest rate for both scenarios overstates how expensive the 15-year option looks relative to the 30-year option.
• Choosing the 15-Year Term on a Tight Budget: A higher required payment with no financial cushion increases the risk of missed payments if income changes.
• Assuming You're Locked In: You can refinance from a 30-year to a 15-year term later (or vice versa) as your finances change — the initial choice isn't necessarily permanent.

Conclusion

There's no universally "right" answer between a 15-year and 30-year mortgage — it depends on your monthly budget, your other financial goals, and how much you value paying less interest versus keeping more flexibility. Run both terms through the calculator above with your actual numbers, compare the monthly payment and total interest side by side, and choose the term that fits your full financial picture, not just the sticker price.