15-Year vs 30-Year Mortgage Calculator
Compare a 15-year and a 30-year mortgage: monthly payments, total interest, the balance left at year 15, what investing the payment difference would earn, and the cost of overpaying a 30-year instead.
| 30-year payment | — |
|---|---|
| 15-year payment | — |
| Extra per month for the 15-year | — |
| 30-year total interest | — |
| 15-year total interest | — |
| Balance after 15 years on the 30-year loan | — |
| Invest the difference instead (30-year + investing) | — |
| 30-year loan paid as if 15 (same rate, extra principal) | — |
| Verdict | — |
In short
A 15-year mortgage has a higher payment but far less interest: 360,000 at 5.9% over 15 years costs 3,018 a month and 183,000 interest, against 2,275 and 459,000 at 6.5% over 30 years. Investing the 743 difference at 6% grows to about 213,000 by year 15, less than the 261,000 still owed on the 30-year, so the 15-year wins unless returns are much higher.
Who this is for: Buyers and refinancers choosing a term, and anyone tempted to invest the difference.
15-year vs 30-year: the trade-off
| 15-year | 30-year | |
|---|---|---|
| Payment | Much higher (typically 40–50% more) | Lower — easier to qualify |
| Rate | Lower | Higher |
| Total interest | Roughly half or less | Often exceeds the amount borrowed |
| Flexibility | Committed to the high payment | Can overpay in good years, drop back in bad ones |
| Equity | Builds fast — useful for moving or refinancing | Slow in the first decade |
The honest comparison is not just interest: the 30-year borrower has extra cash each month. If it is invested and earns more than the mortgage rate after tax, the 30-year can come out ahead — the calculator shows that case explicitly so you can judge whether you would really invest it.
See also: Mortgage Refinance Calculator, Mortgage Payment Calculator (PITI).
Assumptions
- Both payments from the amortising formula on the same principal at their own rates.
- Invest-the-difference: the payment gap compounded monthly at the return for 180 months, compared with the 30-year balance at month 180.
- As-if-15: the 30-year loan paid at the 15-year payment until cleared.
Worked example
30-year: 2,275 a month, 459,200 interest. 15-year: 3,018 a month, 183,300 interest — saves about 275,800. The 743 difference invested at 6% grows to about 213,000 by year 15, against a 30-year balance of 261,200 still owed — so the 15-year is ahead by about 48,000 even after investing. Paying 3,018 on the 30-year loan instead clears it in 16 years 1 month with about 37,000 more interest than the true 15-year — the price of keeping the option to stop.
Frequently asked questions
Is a 15-year mortgage worth it?
If you can comfortably afford the payment and still save for retirement, yes — it is a guaranteed return at the mortgage rate. If the payment would squeeze you, take the 30-year and overpay.
Can I get a 15-year payoff on a 30-year loan?
Yes, by paying extra principal; you give up the lower 15-year rate but keep the option to stop. The calculator shows the cost of that flexibility.
Which has the lower rate?
15-year loans — lenders price them 0.5–0.8 points lower because they carry less interest-rate risk.
Does this work for UK or UAE mortgages?
Yes — it is the same arithmetic for any two terms; enter 25-year vs 15-year rates if those are your options.
How much more is a 15-year payment?
Typically 30–45% more than the 30-year payment on the same loan, offset slightly by the lower 15-year rate.
Can I switch from 30 to 15 years later?
Yes, by refinancing or simply paying the 15-year amount each month; the second option keeps flexibility but at the higher 30-year rate.
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