15 vs 30 Year Mortgage Calculator
Compare the monthly payment, total interest, and total cost of a 15-year vs 30-year mortgage side by side.
With a 30-year mortgage, you pay $626/mo less. What if you invested that difference?
15-year loans pay off interest faster, so the deduction is larger early on but disappears sooner. 30-year loans deduct more total but over more years.
How to Use This 15 vs 30 Year Calculator
Enter your Loan Amount and set separate rates for each term. Rates typically differ — 15-year mortgages usually carry rates 0.5–0.75% lower than 30-year. This rate difference is built into the default values but you can adjust both to match quotes you've received.
The two result cards show both scenarios simultaneously. The green savings panel below summarizes the key tradeoffs: how much more per month the 15-year costs versus how much total interest you save.
The Math Behind the Comparison
15-Year: n = 180 months
30-Year: n = 360 months
Total Interest = (Monthly Payment × n) − Principal
Total Cost = Principal + Total Interest
For a $300,000 loan: At 6.25% (15-yr), payment = $2,572 and total interest = $162,960. At 6.75% (30-yr), payment = $1,946 and total interest = $400,560. The 15-year costs $626 more per month but saves $237,600 in total interest — and builds equity twice as fast.
Example: The Tradeoff Decision
Two Paths to the Same $300,000 Home
| 15-Year at 6.25% | 30-Year at 6.75% | |
| Monthly Payment | $2,572 | $1,946 |
| Monthly Difference | +$626 | — |
| Total Payments | $462,960 | $700,560 |
| Total Interest | $162,960 | $400,560 |
| Interest Saved | $237,600 | — |
| Paid Off | 15 years | 30 years |
| Equity at Year 10 | ~$210,000 | ~$120,000 |
The 15-year borrower pays $626 more per month but owns the home outright 15 years earlier and saves nearly a quarter million dollars in interest. The 30-year borrower has better monthly cash flow, which they could invest — but they'd need to consistently earn 6.75%+ to match the mortgage savings.