15-Year vs. 30-Year Mortgage: The Real Cost Difference
Published 2026-07-31 · Migrify.AI
On a $340,000 loan, the choice between a 15-year and a 30-year term changes your monthly payment by hundreds of dollars — and your lifetime interest by six figures.
The head-to-head numbers
15-year loans price lower than 30-year loans. Using typical spreads (6.66% for the 30-year, 5.95% for the 15-year) on a $340,000 loan:
- 30-year: about $2,185/month principal & interest, and roughly $446,575 in total interest over the life of the loan.
- 15-year: about $2,860/month — $675 more per month — but only about $174,789 in total interest.
That's a lifetime savings of roughly $271,787 for committing to the higher payment. Run your own loan amount through our free mortgage calculator — the amortization chart makes the difference vivid: on a 30-year loan, your early payments are mostly interest for a full decade.
Why the 30-year still wins for most buyers
- Flexibility. The lower required payment is a safety margin. You can always pay a 30-year loan on a 15-year schedule — but you can't pay a 15-year loan on a 30-year schedule when money gets tight.
- Qualification. Lenders qualify you on the required payment, so a 30-year term supports a higher purchase price.
- Opportunity cost. The extra $675/month invested elsewhere may out-earn the mortgage rate you'd save.
When the 15-year makes sense
Choose 15 years when the payment fits under the 28% housing-cost guideline with room to spare, your emergency fund is fully stocked, and you value a guaranteed, tax-free "return" equal to your mortgage rate. It's also popular with refinancers who are years into a 30-year loan and don't want to reset the clock.
A middle path: take the 30-year for safety and add one extra principal payment a year — that alone typically shaves 4–5 years off the loan.
Run your own numbers: the free Migrify.AI calculator shows your full payment — taxes, insurance, and PMI included — in seconds, with no sign-up and no credit impact.