Formulas and 2026 figures checked & updated: July 2026
How to Use the 15-Year vs 30-Year Mortgage Calculator
- Enter the home price and the down payment you're planning to make.
- Enter the interest rate quoted for the 15-year term — typically the lower of the two rates.
- Enter the interest rate quoted for the 30-year term.
- Add estimated annual property tax and homeowners insurance so the comparison reflects your full monthly housing payment, not just principal and interest.
- Compare the monthly principal & interest for each term side by side.
- Review the total interest saved by choosing the 15-year term over the life of the loan.
- Weigh the higher 15-year payment against the interest savings to decide which term fits your budget. Example: on a $320,000 loan, a 15-year term at 6.0% runs about $2,700/month in principal and interest versus roughly $2,075/month for a 30-year term at 6.75% — a $625/month difference — but the 15-year loan pays off in half the time and saves roughly $261,000 in total interest.
What This Calculator Does
The 15-Year vs 30-Year Mortgage Calculator compares two complete amortization schedules — one for a 15-year fixed-rate mortgage and one for a 30-year fixed-rate mortgage — so you can see, side by side, exactly how loan term changes your monthly payment, your total interest paid, and how quickly you build home equity. Instead of guessing at the trade-off, the calculator runs the standard fixed-rate mortgage formula twice, once at each term's typical rate, using the same home price, down payment, property tax, and insurance for both scenarios so the comparison stays apples-to-apples.
The result is driven by the home price, down payment, and the interest rate quoted for each term, plus estimated property tax and insurance. Because lenders take on less repayment risk over a 15-year period, 15-year fixed rates are typically priced about 0.5 to 0.75 percentage points below 30-year fixed rates — for example, a 30-year loan quoted at 6.75% might pair with a 15-year loan around 6.0%. That lower rate compounds with a shorter amortization schedule to produce dramatically less total interest: on a typical $320,000 loan, a 15-year term often cuts total interest by more than half compared to a 30-year term, even though the required monthly payment runs several hundred dollars higher.
Buyers use this calculator when deciding how to structure a home purchase or a refinance. Those who prioritize the lowest possible monthly payment and maximum cash-flow flexibility usually lean toward a 30-year term, while buyers who can comfortably afford a higher payment and want to be mortgage-free faster — while saving tens or hundreds of thousands of dollars in interest — lean toward a 15-year term. It's also useful for evaluating a middle path, such as keeping a 30-year loan but making extra principal payments to approximate a 15-year payoff timeline without locking in the higher required payment. Running both scenarios side by side before signing a loan estimate helps you negotiate from an informed position rather than relying on a lender's default recommendation.
Formula
M = P[r(1+r)ⁿ] / [(1+r)ⁿ − 1]Standard fixed-rate amortization, run once for n = 180 months (15 years) and once for n = 360 months (30 years), each at its own rate.
- PLoan principal (home price − down payment)
- rMonthly interest rate (annual rate ÷ 12)
- nTotal number of monthly payments
Examples
Example 1: $400,000 home, 20% down
$320,000 loan. 15-year at 6.0% vs. 30-year at 6.75%.
The 15-year payment is about $2,700/month versus about $2,075/month for the 30-year term — a $625/month difference — but the 15-year loan pays off in half the time and saves roughly $261,000 in total interest ($166,000 vs. $427,000).
Example 2: $250,000 home, 10% down
$225,000 loan. 15-year at 6.0% vs. 30-year at 6.75%.
The 15-year payment is about $1,899/month versus about $1,459/month for the 30-year term — a $440/month difference — with roughly $183,500 saved in interest over the life of the loan.
Example 3: $600,000 home, 20% down
$480,000 loan. 15-year at 6.0% vs. 30-year at 6.75%.
The 15-year payment is about $4,051/month versus about $3,113/month for the 30-year term — a $938/month difference — saving roughly $391,500 in total interest by choosing the shorter term.
Key Terms Explained
- Amortization
- Paying off a loan through fixed payments over time. Early payments are mostly interest; later payments are mostly principal as the balance shrinks.
- Interest Rate
- The percentage a lender charges on the principal, before fees. Unlike APR, the interest rate alone doesn't include origination or other loan costs.
- Principal
- The original amount borrowed or invested, before interest. Each loan payment is split between paying down principal and paying interest.
- Down Payment
- The upfront cash you pay toward a purchase, reducing the amount financed. A larger down payment lowers monthly payments and can avoid PMI.
- Loan Term
- The length of time you have to repay a loan. A longer term lowers the monthly payment but increases the total interest paid.
- Home Equity
- The share of your home you actually own: its market value minus the balance you still owe on the mortgage.
Continue Your Financial Planning
Methodology
Each term is calculated independently using the standard fixed-rate amortization formula, M = P[r(1+r)ⁿ]/[(1+r)ⁿ−1], at its own rate and number of payments (180 months for 15 years, 360 for 30 years). The 15-year term typically uses a lower rate to reflect reduced lender risk, entered separately so you can match your actual loan quotes, and estimated property tax and insurance are added to each result to show a full monthly PITI payment.
Frequently Asked Questions
Is a 15-year or 30-year mortgage better?+
A 15-year mortgage has a higher monthly payment but a lower interest rate and far less total interest — often saving over half of what you'd pay over 30 years. A 30-year mortgage has a lower monthly payment, giving you more budget flexibility and cash to invest elsewhere.
How much lower is the rate on a 15-year mortgage?+
15-year mortgages typically carry a rate about 0.5-0.75 percentage points lower than 30-year mortgages, since lenders take on less risk over a shorter term.
Can I get 15-year benefits with a 30-year loan?+
Partially — you can make extra principal payments on a 30-year loan to pay it off faster and save interest, while keeping the lower required payment as a safety net. You won't get the lower 15-year rate, but you gain flexibility a 15-year loan doesn't offer.
How much faster do I build equity with a 15-year mortgage?+
Because more of each monthly payment goes toward principal on a shorter term, equity builds noticeably faster. In the first five years, a 15-year loan typically pays down two to three times more principal than a 30-year loan on the same starting balance, even before accounting for the lower 15-year rate.
Can I switch from a 30-year to a 15-year mortgage later?+
Yes, through refinancing. Many homeowners start with a 30-year mortgage for lower payments and flexibility, then refinance into a 15-year loan once income rises or rates drop. This resets the amortization schedule and typically requires new closing costs, so it's worth comparing the new payment and total interest against your remaining loan term first.
What credit score do I need to qualify for a 15-year mortgage?+
Lenders generally apply similar minimum credit score requirements to 15-year and 30-year mortgages — often around 620 for conventional loans — but the higher required monthly payment on a 15-year term means lenders will also scrutinize your debt-to-income ratio more closely to confirm you can comfortably afford it.
Can I save my results?+
Yes. Use “Save results” to store a snapshot. Without an account it remains in this browser. If you log in, saved scenarios sync securely to your SmartRates account so they are available on your other devices.
How do I share my calculation?+
Click “Share” in the toolbar to copy a link (or open your device’s share sheet). The link encodes your exact inputs, so whoever opens it sees the calculator pre-filled with the same numbers and the same result.
Can I email my calculator results?+
Yes. Click “Email results” to open your default email application with the current inputs, results, and calculator link already included. Review the message and choose the recipient before sending.
Can I export or print my results as a PDF?+
Yes. Click “Export PDF” to open a clean, printable summary of your inputs and results that you can save as a PDF or print. It includes a timestamp and a link back to the calculator.
How accurate are the calculator results?+
The arithmetic follows the formula and assumptions documented on this page. The result is still an estimate because actual rates, fees, taxes, timing conventions, eligibility rules, and provider calculations can differ. Use figures from your official quote, statement, contract, or tax form before making a financial decision.
Which inputs have the biggest effect on the result?+
Rate, time, starting balance, recurring payments or contributions, and fees usually have the largest effects. Change one input at a time to create a conservative, expected, and optimistic scenario instead of relying on a single forecast.
Are taxes, fees, and inflation included?+
Only when they appear as an input or are explicitly described in the methodology. Do not assume an omitted cost is zero. Review the formula and methodology sections to see exactly what is included before comparing the result with an outside quote.
Can this calculator predict future rates or returns?+
No. A calculator projects the assumptions entered; it cannot predict market returns, inflation, variable interest rates, tax-law changes, or provider decisions. Rerun the calculation with several assumptions to understand the range of possible outcomes.
Why might my lender, bank, broker, or tax software show a different result?+
Professional systems may use daily timing, transaction dates, compounding conventions, rounding rules, account-specific fees, credits, eligibility details, or regulations that a general-purpose calculator cannot know. A small difference can be rounding; a large difference usually means an assumption or included cost is different.
Disclaimer: Calculations are for informational purposes only and do not constitute professional financial advice. Please consult with a certified professional before making financial decisions.