Take the 15 if the payment is comfortable
If the higher payment still leaves you funding retirement, keeping an emergency fund and carrying no expensive debt, the 15-year loan is the cheapest way to own the house and the discipline is built in.
15 vs. 30 Year Mortgage Calculator
The shorter loan costs far less. The longer loan buys flexibility. And there is a third route most comparisons leave out: take the 30-year loan and pay it like a 15.
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Three ways to borrow the same money
Principal and interest only. Property taxes, homeowners insurance, PMI and HOA dues are not included.
Or: take the 30 and invest the difference
Same money out of pocket every month for 30 years. In one path the loan is gone in 15 and the payment is invested afterwards; in the other the payment difference is invested from day one.
The asymmetry to remember: the interest you avoid by taking the 15-year loan is guaranteed. The investment return is an average that includes years when the market falls by a third. When the two numbers are close, they are not really close.
What the shorter term really buys
Two forces work together on a 15-year loan. The obvious one is time: half as many months of interest. The less obvious one is the rate itself, which is typically a half point or more below the 30-year rate because the lender is exposed for less time. Together they usually cut lifetime interest by well over half, which is why the difference in the table above is so much larger than people expect.
The cost is rigidity. A 15-year payment is roughly 40–50% higher, and it is a contractual obligation, not an intention. Job loss, a medical bill or a bad year in a business hits exactly as hard whether or not you were ahead of schedule. That is the case for the third column: a 30-year loan paid voluntarily at the 15-year amount reaches almost the same place, and in a bad month you simply pay the required amount and nobody needs to be told.
When each one is the right answer
Take the 30 if it is tight
A payment that only works when everything goes right is a payment that does not work. Take the lower obligation, then send extra whenever you can. The flexibility costs you the rate difference, which is a fair price.
Take the 30 if you have better uses first
Employer 401(k) match, high-interest debt and a cash cushion all outrank prepaying a mortgage. Do those first with the payment difference, then decide.
Whatever you choose, the same principle applies afterwards: extra money sent to a U.S. mortgage goes to principal and shortens the loan without lowering the required payment. The main payoff calculator shows exactly what any extra amount does to the loan you end up with.
Frequently asked questions
Is a 15-year mortgage always better than a 30-year?
It is always cheaper in total interest, but cheaper is not the same as better. A 15-year loan commits you to a much higher required payment for fifteen years, and that obligation does not care whether you lose your job. A 30-year loan paid voluntarily like a 15 gets you most of the saving while leaving you the option to fall back to the lower payment in a bad year.
Why is the 15-year interest rate lower?
Lenders take less risk over a shorter horizon, so 15-year rates in the United States are usually around half a percentage point to three quarters of a point below 30-year rates. That gap is part of why the total interest difference is so large, and it is why this calculator asks for both rates separately instead of assuming they are the same.
What does taking the 30 and paying it like a 15 actually cost?
A little more than the real 15-year loan, because you pay the higher 30-year rate on the balance. The calculator shows the exact gap for your numbers. In exchange you keep the right to stop the extra payment at any time, which is a genuine form of insurance with a measurable price.
Should I invest the difference instead of taking the 15?
That is the honest alternative, and the comparison above runs it with the same money leaving your pocket each month. Investing has the higher expected return but it is not guaranteed, while the interest you avoid on the mortgage is certain. If the two numbers come out close, the guaranteed one is worth more than the arithmetic suggests.
Can I refinance from a 30 to a 15 later?
Yes, and people often do once their income rises. Remember it is a new loan with closing costs and a new clock, so compare it against simply paying extra on your existing loan, which costs nothing to start and nothing to stop.
More calculators
Extra mortgage payment calculator
The main tool: extra payments, recast, payoff-vs-invest, biweekly, PMI removal and the full amortization schedule in one place.
Biweekly payment calculator
What paying half your mortgage every two weeks really does, and the free way to get the same result.
Refinance break-even calculator
How many months until a refinance pays for itself, and why a lower rate can still cost you more.
How this is calculated
Both loans are amortized with the standard fixed-rate formula at the rate you enter for each term, and the investment comparison holds the monthly cash outlay identical in both paths. Every formula on this site is published in plain English on the methodology page, including a worked example you can verify by hand.
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These results are estimates, not financial advice. They depend entirely on the figures you enter and exclude taxes, insurance, PMI, HOA dues and any lender fee. Confirm your actual terms with your servicer and speak to a licensed professional before acting. Read the full disclaimer.