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Calculator results are estimates for planning, not a loan approval, commitment, rate lock, or Loan Estimate.
What the 15-year vs. 30-year calculator calculates
This tool compares the same loan amount financed two ways: a 15-year term and a 30-year term, showing the monthly payment difference and the total interest saved by choosing the shorter term.
A 15-year mortgage pays off faster and typically carries a lower interest rate than a 30-year, but the tradeoff is a meaningfully higher required monthly payment, since the same balance is amortized over half the time.
The calculator frames the decision as a specific dollar tradeoff: how much extra you'd pay monthly on the 15-year option, against how much total interest that extra payment saves you over the life of the loan.
How to use it, step by step
- 1Enter the loan amount you're comparing — the same amount is used for both the 15-year and 30-year scenarios.
- 2Enter an interest rate to test for each term. Since 15-year rates are typically somewhat lower than 30-year rates, consider testing a slightly lower rate on the 15-year side if you have real quotes to reference.
- 3Review the extra monthly payment required for the 15-year option compared to the 30-year option.
- 4Review the total interest saved over the life of the loan by choosing the 15-year term.
- 5Weigh the higher required payment against your monthly budget, and consider whether making extra payments on a 30-year loan could achieve a similar result with more flexibility (see the extra payment calculator).
A worked example
Example inputs
- Loan amount
- $350,000
- 30-year rate (example only)
- 6.75%
- 15-year rate (example only)
- 6.0%
Result
The 30-year payment on $350,000 at the illustrative 6.75% rate runs meaningfully lower per month than the 15-year payment at the illustrative 6.0% rate — but the 15-year loan pays off in half the time.
Because the 15-year loan accrues far less total interest over its shorter life, the lifetime interest savings compared to the 30-year option can run well into six figures on a loan this size, even though the 15-year rate is only modestly lower.
The rates above are illustrative example inputs only, not current quotes.
How to read the result
The extra monthly payment for the 15-year option is the real cost of that interest savings — make sure it's genuinely comfortable in your budget, not just affordable on paper.
Total interest saved is the clearest way to see the long-run value of the shorter term, since it strips out the psychological pull of a lower rate and shows the actual dollar impact.
A 15-year loan forces the faster payoff; a 30-year loan with voluntary extra principal payments can approach similar savings while keeping the lower required payment as a safety net in a tight month.
Common mistakes
- Choosing a 15-year term because the rate looks better, without confirming the higher required payment fits comfortably in the monthly budget, including in a tighter-income month.
- Assuming a 30-year loan is always the 'expensive' option — with disciplined extra principal payments, a 30-year loan can closely approach 15-year interest savings while keeping payment flexibility.
- Comparing the two terms at the same interest rate when quoting real loans — 15-year rates are typically priced somewhat lower than 30-year rates for the same borrower.
- Not considering opportunity cost — money directed to extra principal on a 15-year loan isn't available for other goals like retirement contributions or an emergency fund.
Related guides
- Extra Payment Calculator
- 15-Year vs. 30-Year Comparison
- Mortgage Payment Calculator
- Glossary: Interest Rate
Frequently asked questions
Not necessarily — it depends on whether the higher required payment fits your budget comfortably. A 15-year loan saves substantial interest and builds equity faster, but a 30-year loan offers more monthly flexibility, which matters if your income varies or you have other financial priorities.
Typically, yes — 15-year mortgages are usually priced with a somewhat lower interest rate than 30-year mortgages for the same borrower, since the lender's risk is spread over a shorter period. The exact difference varies by lender and market conditions.
Yes — making extra principal payments on a 30-year loan can shorten the effective payoff time and cut total interest substantially, while keeping the lower required minimum payment as flexibility. The extra payment calculator models this directly.
It depends on the loan amount and rates, but the 15-year payment is typically meaningfully higher — often 40% to 60% more per month than the 30-year payment on the same loan amount, since the balance amortizes over half the time.
Yes. Because a larger share of each 15-year payment goes to principal from the start, and the loan pays off in half the time, equity builds noticeably faster than on a 30-year loan with the same starting balance.