15 vs 30 Year Mortgage: Payment, Interest, and How to Choose

The core trade-off

A 15-year mortgage usually has a higher monthly payment and a lower total interest bill. A 30-year mortgage usually has a lower payment and higher lifetime interest, with more flexibility for cash flow. Neither is automatically “better”—the right term depends on budget stability, other goals (retirement, emergency reserves), and how long you expect to keep the home.

Payment and interest, side by side

On the same loan amount and rate, cutting the term roughly in half raises the required principal portion each month, so the payment jumps. Because you repay faster, cumulative interest falls sharply. If the 15-year payment crowds out savings or necessary spending, the interest savings may not be worth the strain.

A middle path many households use

Some borrowers choose a 30-year loan for payment flexibility, then send voluntary extra principal when cash flow allows. That can shorten the effective term without locking in the higher required payment of a 15-year note. Model required payments and extra-payment scenarios in the mortgage calculator.

Questions to ask yourself

• Can I still fund emergency savings at the higher 15-year payment?
• Do I expect income to rise, stay flat, or become less predictable?
• Am I optimizing for lowest interest or lowest required payment?
• Will I likely sell before either term ends?

Run both terms at realistic rates and tax/insurance assumptions, then choose the payment you can sustain—not only the one that looks best on total interest.