15 vs 30 Year Mortgage Calculator
Enter the loan and both rates. See the payment gap, the enormous interest difference — and the honest third option: taking the 30 and investing the difference.
| 15-year | 30-year | |
|---|---|---|
| Monthly payment | — | — |
| Total interest | — | — |
| Interest saved by the 15 | — | |
| 30-yr + investing the gap at 7% | — | |
The trade in one sentence
On $300,000, the 15-year costs about $740/month more but saves roughly $250,000 of interest — the classic argument for it. The counter-argument: invest that $740/month at 7% instead and after 30 years the portfolio (~$880,000) far exceeds the interest saved.
Why people still choose the 15
- Guaranteed vs hoped-for: the interest savings are certain; the 7% market return is not.
- Behavior: most people do not actually invest the difference — it evaporates into spending. The 15-year is forced discipline.
- Rate discount: 15-year loans price 0.5–0.75 points lower.
- Debt-free date: owning your home outright at 45 instead of 60 changes career and retirement options in ways spreadsheets undercount.
The middle path most people miss
Take the 30-year, pay it like a 15 when you can, drop to the required payment when life happens. You give up the rate discount but keep the flexibility — model it with the extra payment calculator.
Frequently asked questions
How much more is a 15-year mortgage payment?
On $300,000 at typical rates, roughly $700–800/month more than the 30-year. In exchange, total interest drops by around $250,000.
Is a 15-year mortgage worth it?
If the higher payment fits under ~28% of income and you still max retirement savings — strongly yes. If it crowds out investing or your emergency fund, the 30-year with voluntary extra payments is safer.
Why are 15-year rates lower?
Shorter loans carry less inflation and default risk for the lender, so they price 0.5–0.75 percentage points below 30-year loans.
Can I turn a 30-year into a 15?
Effectively yes — pay the 15-year payment amount on a 30-year loan and it retires in about 16 years (the small difference is the rate premium). You keep the option to pay less in hard months.
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Last updated: 2026-07-08