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Results are hypothetical illustrations based on the numbers you enter and simple assumptions: constant rates and returns, with no taxes or fees unless stated. They are not predictions or guarantees; real returns vary and can be negative. Educational content only. Not financial advice. Examples are hypothetical, not guaranteed. See our Disclaimer.
Quick answer: On a hypothetical $400,000 loan at 6.00% for 15 years vs 6.75% for 30 years, the 15-year payment is $3,375.43 a month against $2,594.39: about $781 more a month, but it saves $326,404 in interest. Hypothetical rates, not a quote, and not guaranteed.
What this 15 vs 30 year mortgage calculator does
It puts the two most common fixed-rate loans side by side: the monthly payment for each, the total interest for each, and the difference. An optional line answers the classic follow-up: what if you take the 30-year and invest the payment difference instead?
How to use it
- Enter the loan amount (price minus down payment).
- Enter the 30-year rate and the 15-year rate; 15-year loans usually carry a lower rate.
- Optional: set an investment return for the “invest the difference” line, or 0% to hide it.
Payments are principal and interest only; property tax, insurance and PMI come on top for both loans.
From the channel
Worked example
Inputs: $400,000 loan, 30-year at 6.75%, 15-year at 6.00%, invest-the-difference return 7%.
| 15-year (6.00%) | 30-year (6.75%) | Difference | |
|---|---|---|---|
| Monthly payment | $3,375.43 | $2,594.39 | $781.03 |
| Total interest | $207,577 | $533,981 | $326,404 |
| Total paid | $607,577 | $933,981 | $326,404 |
Invest the difference: putting the $781.03 a month into investments at 7% for 15 years grows to about $247,559. At that point the 30-year loan still owes $293,182, so in this example the 30-year plus investing is about $45,623 behind the 15-year at year 15 (hypothetical, before taxes). With both loans at 6.00% the gap is $255,776 in interest, the number from our video, and investing the $977.23 difference comes out about $25,548 ahead. The rate spread and your return decide it.
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Questions people ask
Is a 15-year or 30-year mortgage better?
A 15-year costs far less interest ($326,404 less in our $400,000 example) but has a higher payment (about $781 more a month). A 30-year is easier on cash flow and leaves room to invest or build savings. Pick the payment you can carry comfortably.
How much more is a 15-year mortgage payment?
Usually 25-45% more. On $400,000, a 15-year at 6.00% is $3,375.43 a month vs $2,594.39 for a 30-year at 6.75%, a difference of about $781.
Do 15-year mortgages have lower interest rates?
Usually, yes. Lenders charge less for the shorter term, and the 15-year average rate in Freddie Mac’s weekly survey typically sits well below the 30-year. Compare real quotes for both terms on the same day.
Should I get a 30-year mortgage and invest the difference?
It only works if you really invest the difference every month and earn more than your rate. In our example (7% return) the 30-year plus investing is about $45,623 behind at year 15; with both loans at 6% it is about $25,548 ahead. Hypothetical, not guaranteed.
Can I pay off a 30-year mortgage in 15 years?
You can get close by paying extra. Paying the 15-year amount ($3,375.43) on a 6.75% 30-year loan pays it off in about 16 years 4 months, with roughly $53,375 more interest than the 15-year loan, but you keep the option to pay less in a tight month.
How much income do I need for a 15-year mortgage?
Using the common 28% guideline for principal and interest alone, a $3,375.43 payment needs about $144,661 a year of gross income, vs about $111,188 for the 30-year payment of $2,594.39. Taxes and insurance raise both.