15-Year vs 30-Year Mortgage: Key Differences

A 15-year mortgage and a 30-year mortgage are both fully amortizing loans. The difference is how quickly you repay principal — and how much interest you pay along the way. This guide compares the tradeoff so you can use the mortgage payment calculator with a realistic picture of cash flow versus total cost.

What actually changes

Lengthening the term lowers the required monthly principal-and-interest (P&I) payment because you spread the same loan over more months. Shortening the term raises the monthly P&I payment and reduces the number of months interest can accrue. Taxes, insurance, HOA, and PMI are separate from this comparison; they do not automatically change just because you chose 15 or 30 years.

Lenders price 15-year loans at a lower note rate than 30-year loans more often than not, because the credit risk period is shorter. That rate difference is a quote, not a rule. Do not assume a specific spread when you plan.

Worked example (illustrative)

The figures below use an example $300,000 loan at a 6.75% note rate for both terms. Using the same rate isolates the term effect. In a real quote, the 15-year rate may be lower.

• 30-year P&I: about $1,946 per month, 360 payments.
• 15-year P&I: about $2,655 per month, 180 payments.
• Monthly cash-flow difference: roughly $709 more on the 15-year loan.
• Lifetime interest is substantially lower on the 15-year schedule because the balance declines faster and the loan ends 15 years sooner.

Recalculate with your actual quoted rates on the mortgage calculator with taxes, insurance, and PMI. If you also want to see how extra principal on a 30-year loan can mimic a shorter term, read how extra mortgage payments reduce interest.

Tradeoffs that matter

The 30-year payment is easier to carry if income is tight, reserves are thin, or you want leftover cash for other goals. That flexibility has a cost: more months of interest. The 15-year payment is a harder monthly commitment. Missing that payment is not an academic problem — it is a default risk. A loan you can actually pay is better than a cheaper-interest loan you cannot sustain.

Prepaying a 30-year mortgage is optional; the 15-year payment is required. If you like the idea of a shorter loan but want the option to pay less in a bad month, a 30-year term with extra principal can be more resilient than locking the higher required payment.

When the choice is close

Compare after-tax cash flow, not just P&I. If you itemize, mortgage interest may be deductible subject to IRS rules and your tax situation — that does not make the 30-year loan “free.” Also compare how long you expect to keep the loan. If you are likely to sell or refinance in a few years, the early-year interest difference is smaller than a full-term comparison implies.