15-Year vs 30-Year Mortgage: The Real Cost Difference, With Numbers
This guide is for education and planning. It is not financial advice. Rates, taxes and your own situation change the answer, so confirm figures with a lender or a licensed financial adviser before committing.
The Short Version
A 15-year mortgage costs more each month and far less overall. A 30-year mortgage keeps the payment lower and leaves more room for savings, emergencies and other goals, but you pay substantially more interest. Which is better depends less on the math than on how secure your income is and what you would actually do with the monthly difference.
Side by Side: $300,000 at October 2026 Rates
The example uses Freddie Mac's Primary Mortgage Market Survey for the week of October 1, 2026: 7.28% for a 30-year fixed and 6.60% for a 15-year fixed. Those are national averages for borrowers with 20% down and excellent credit, not a quote. Your rate may differ.
| $300,000 loan | 30-year at 7.28% | 15-year at 6.60% | Difference |
|---|---|---|---|
| Monthly principal and interest | $2,052.64 | $2,629.84 | 15-year costs $577.20 more per month |
| Total interest over the loan | $438,949 | $173,372 | 15-year saves about $265,578 |
| Interest paid in first 5 years | $106,382 | $88,362 | $18,020 less |
| Principal repaid after 5 years (equity from payments) | $16,776 | $69,428 | About 4 times as much |
| Balance after 5 years | $283,224 | $230,572 | $52,652 lower |
Two effects stack up for the 15-year loan: a lower rate (lenders charge less for shorter terms) and half as many years of interest. After five years, the 30-year borrower has paid more than $123,000 in total and reduced the balance by less than $17,000. The amortization guide explains why early payments are mostly interest.
The Opportunity-Cost Argument
The usual case for the 30-year loan: take the lower payment and invest the $577.20 difference. To test it fairly, assume both households spend exactly $2,629.84 a month on housing plus investing for 30 years:
- Household A takes the 15-year loan. After it is paid off, it invests the full $2,629.84 every month for the remaining 15 years.
- Household B takes the 30-year loan and invests $577.20 every month for all 30 years.
Assumptions: a constant annual return after taxes and fees, compounded monthly, no missed contributions, and no other differences in tax treatment. Both homes are paid off at year 30.
| Annual return | Household A investments at year 30 | Household B investments at year 30 | Ahead |
|---|---|---|---|
| 4% | $643,409 | $395,542 | A by about $248,000 |
| 6% | $754,533 | $562,494 | A by about $192,000 |
| 8% | $887,851 | $813,023 | A by about $75,000 |
At these rates, the break-even is about 8.8% a year after taxes and fees, sustained for 30 years, with every dollar of the difference invested. That is a high bar. The argument for investing the difference is much stronger when the 30-year rate is low or when the gap between the two rates is small. Rerun the comparison with your actual quotes.
What the table cannot capture: Household B has far more flexibility. If a job is lost, B can stop investing for a while; A must keep paying $2,629.84 or risk the home. B also has liquid savings available for emergencies, while A's wealth sits in home equity until the house is sold or borrowed against.
The Middle Path: a 30-Year Loan Paid Like a 15-Year
You can take the 30-year loan and voluntarily pay more, keeping the right to fall back to the required payment. On the same $300,000 at 7.28%:
| Payment on the 30-year loan | Paid off in | Total interest |
|---|---|---|
| Required $2,052.64 | 30 years | $438,949 |
| $2,352.64 (+$300) | about 20.5 years | $277,802 |
| $2,552.64 (+$500) | about 17.3 years | $226,805 |
| $2,629.84 (same as the 15-year payment) | about 16.3 years | $212,131 |
Paying the 15-year amount on a 30-year loan costs about $38,800 more interest than the true 15-year loan, because of the higher rate. That is the price of flexibility. Check that your lender has no prepayment penalty and applies extra payments to principal.
What the Calculator Leaves Out
- Property taxes and homeowners insurance, often collected monthly through an escrow account. They can add hundreds of dollars a month and rise over time.
- Private mortgage insurance (PMI) on conventional loans with less than 20% down. The CFPB explains how it works and when it can be removed. Because the 15-year loan builds equity faster, PMI usually ends sooner.
- Closing costs and points, listed on the Loan Estimate each lender must provide. Compare offers using APR, not only the rate.
- HOA dues, maintenance and repairs, which do not depend on the loan term.
- Tax effects. Mortgage interest is deductible for some US borrowers who itemize. Most households take the standard deduction, so check your own situation.
Decision Checklist
- Can you afford the 15-year payment plus taxes and insurance with room to spare?
- Do you have an emergency fund of several months of expenses after the down payment and closing costs?
- Is your income stable, or does it vary with commissions, contracts or seasonal work?
- Do you have higher-interest debt (cards, car loans) that should be paid first?
- Are you contributing enough to retirement accounts to receive any employer match?
- How long do you expect to stay in the home? If it is under about five years, the term affects equity but the rate and closing costs may matter more.
If most answers are yes, the 15-year loan's savings are hard to beat. If several are no, the 30-year loan with voluntary extra payments may be the safer choice.
Running the Scenarios in QuickToolApp
- Open the Loan Calculator on the home page.
- Enter 300000, 7.28, 30 and press Calculate. Note Monthly and Total Interest.
- Change only the rate and term to 6.6 and 15. Calculate again.
- Repeat with your own lender quotes, and with a rate 0.5 points higher as a stress test.
The calculator returns principal and interest only, for whole-year terms, and does not model extra payments. Use the tables in this guide or a spreadsheet for the middle-path scenarios, and see the loan estimate guide for a scenario template.