15-Year vs 30-Year Mortgage: The Real Numbers
Choosing between a 15-year and 30-year mortgage is a tradeoff between monthly breathing room and lifetime interest. Here is what the numbers actually look like, and a framework for deciding.
- A 15-year loan typically carries a rate about 0.5–0.75% lower than a 30-year loan.
- On a $300,000 home with 20% down, the 15-year payment is roughly 40% higher — but total interest can be less than half.
- The hybrid strategy: take the 30-year and pay it like a 15-year, keeping the option to fall back.
The headline numbers
Take a $300,000 home with 20% down, so a $240,000 loan. At 6.9% over 30 years the principal-and-interest payment is about $1,582 a month, and total interest over the life of the loan is roughly $329,000 — more than the loan itself.
The same loan at 6.4% over 15 years costs about $2,077 a month, but total interest drops to around $134,000. You pay $495 more per month to save roughly $195,000 in interest. That is the entire decision in one paragraph.
Why the rate difference matters
Lenders price 15-year loans lower because they carry less risk: the money returns faster and default exposure is shorter. The gap varies with the rate environment but is usually between 0.5 and 0.75 percentage points.
That gap does quiet work. Part of the 15-year loan's interest saving comes from the faster payoff, but a meaningful slice comes simply from the lower rate applied to every payment for the whole term.
When the 30-year is the smarter choice
If the 15-year payment forces you to raid savings, skip retirement contributions, or live without an emergency fund, the 30-year is objectively better. Liquidity has value: money in savings can cover a job loss, while extra equity in a house cannot be spent.
The 30-year is also the right tool when your income is variable or early in its growth curve. You can always prepay later; you cannot un-commit to a higher required payment.
The hybrid strategy most advisors actually suggest
Take the 30-year loan for its low required payment, then voluntarily pay the 15-year amount whenever your budget allows. Mathematically this reproduces most of the 15-year loan's interest savings.
The difference is optionality: in a bad month you pay the required minimum and nothing breaks. With a true 15-year mortgage, the higher payment is a legal obligation whether or not the month is bad.
Run your own numbers
The right answer depends on your rate offer, down payment and discipline — all inputs. Use our mortgage calculator to compare both terms side by side with your actual figures, and the loan payment calculator to model the prepayment scenario.
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Frequently asked questions
Is a 15-year mortgage always cheaper overall?
Yes in total interest — the shorter term and lower rate guarantee it. The cost is a monthly payment roughly 40% higher, which is a liquidity and risk tradeoff, not just a math one.
Can I refinance from a 30-year to a 15-year later?
Usually yes, and many borrowers do once income grows. Watch closing costs (2–5% of the loan) and make sure the rate improvement actually justifies them.