Ask a loan officer how much interest a 15-year mortgage saves and you will usually get a percentage. Ask for a dollar figure and the conversation gets a little quieter. That is a shame, because the dollar figure is the whole point.
For most buyers and refinancers right now, a 15-year fixed loan wipes out roughly 60% to 70% of the lifetime interest a 30-year loan would charge. On a $350,000 balance, that lands around $285,000. Not a typo. Six figures, and not the small kind.
The short answer, in dollars instead of percentages
The savings range widely because three things move at once: how much you borrow, how big the rate gap is between the two terms, and how long you actually keep the loan. A $200,000 balance produces a very different answer than a $600,000 one, even at identical rates.
Here is the rough shape of it for a typical borrower putting 20% down:
- $200,000 loan: about $165,000 in interest saved
- $350,000 loan: about $285,000 saved
- $500,000 loan: about $410,000 saved
Those figures assume the 15-year comes with a rate about 0.75 percentage points below the 30-year and that you keep the loan to maturity. Both assumptions matter, and both are worth checking against your own quotes rather than a blog post.
Why the numbers get so large
Two forces stack on top of each other, which is why the savings feel disproportionate.
You pay for half as long
Interest is rent on money you still owe. A 30-year borrower dribbles principal down slowly, so the outstanding balance stays large for a decade or more. A 15-year borrower retires principal about twice as fast, which means there is less money left to charge interest on in every single month after the first.
The rate itself is lower
Lenders price shorter loans cheaper because they carry less risk. Fifteen years of exposure instead of thirty is a meaningful difference to an investor holding the loan. That discount usually runs half a point to three-quarters of a point, though it swings with the market. A closer look at the 15-year versus 30-year rate gap is worth ten minutes if you want to see how that half-point compounds over time.
A $350,000 loan, run both ways
Concrete numbers beat percentages. Say you borrow $350,000. The 30-year is priced at 6.75% and the 15-year at 6.00%.
- 30-year: $2,270 per month principal and interest, $467,200 paid in interest over the life of the loan
- 15-year: $2,954 per month, $181,600 in total interest
- The gap: $684 more per month, $285,600 less interest, and the house is yours 15 years sooner
Look at what happens in month one, because it explains everything that follows. On the 30-year, $1,969 of that $2,270 payment goes to interest and just $301 touches the principal. On the 15-year, $1,750 goes to interest and $1,204 hits the principal. Same house, same day, four times the equity built in a single month.
The payment increase is where the decision actually lives
The $684 difference is not the headline number most people focus on, but it is the one that decides whether this works. A 15-year payment is not a small step up from a 30-year. It is often 30% higher, and lenders qualify you against the full amount including taxes and insurance.
There is a second number that catches people: the cash you need at closing. Prepaids, escrow funding, and lender fees scale with the loan, and a shorter amortization can change how much of your first payment is interest versus principal in ways that feel counterintuitive on paper. The figure a 15-year payment calculator spits out that surprises most buyers is worth understanding before you start touring houses with that budget in your head.
When the shorter term is the wrong tool
A 15-year mortgage is a fantastic product for the right household and a genuinely bad one for others. It tends to backfire when:
- It eats your emergency fund. A $684 monthly increase with $4,000 in savings is a fragile setup. One job loss and the math flips hard.
- Your income is variable. Commission, contract work, or a business with uneven months pairs badly with a fixed payment that is 30% higher.
- You are already behind on retirement. Home equity is illiquid. You cannot spend it at 65 without selling or borrowing against it.
- You are buying a starter home. If you will move in five years, you still save real money, but not the full six figures, and the extra cash could go toward the next down payment.
None of those are reasons to avoid the loan. They are reasons to run the numbers honestly rather than assuming the biggest interest savings on the page is automatically the smartest move.
The middle ground most people never ask about
Terms come in more sizes than 15 and 30, and lenders rarely volunteer that. A 20-year fixed sits close to 15-year pricing in many rate sheets while keeping the payment meaningfully lower. It has become something of a quietly overlooked option that still saves six figures on a typical loan, and it barely shows up in online comparison tools.
A 25-year is the other one worth asking for. You give up some interest savings compared with a 20, but you keep a payment that looks a lot like a 30-year. For buyers who want to accelerate without squeezing the monthly budget, the in-between term is often the honest compromise. Ask for all four quotes. The worst that happens is you learn something.
Testing the “I’ll invest the difference” argument
This comes up in every conversation about shorter terms, and it deserves a real answer rather than a dismissal.
Take that same $684 and put it in an index fund every month for 15 years at a 7% average return. You end up with roughly $216,000 before taxes. Meanwhile the 15-year borrower has banked $285,600 in guaranteed, tax-free interest savings and owns the house outright with 15 years of no payment at all.
On pure arithmetic, the 15-year wins. The 30-year route is not irrational, though. It gives you liquidity, flexibility, and a lower floor if income drops, and a disciplined investor who actually invests the difference and leaves it alone for three decades can close the gap. The catch is behavioral. Most people do not invest the difference. They absorb it into lifestyle, and then they have neither the savings nor the equity.
What to compare before you commit
Get Loan Estimates for both terms on the same day, from the same lender, at the same purchase price. Then look at page three. It shows the Total Interest Percentage, a figure that tells you how much interest you will pay over the life of the loan as a percentage of the amount borrowed. It is the closest thing to an apples-to-apples cost comparison the disclosure offers.
Beyond that, ask three questions. What is my payment if taxes and insurance rise 20%? How many months of expenses would I have left in savings after closing? And if I lose this job, how long can I carry this payment while I find another one?
If the answers feel comfortable, the 15-year is very likely the better financial move, and the $285,000 on a $350,000 loan is real money that never leaves your pocket. If they do not, take the 30-year and pay extra when you can. You keep the interest savings in proportion to the extra you send, and you keep the flexibility to stop in a bad month. Either way, get both sets of numbers in writing, side by side, before you sign anything. That is when the question of how much interest a 15-year mortgage saves stops being abstract.