The short answer
On a 30-year mortgage, you'll usually pay more in interest than you borrowed. A $400,000 loan at 6.5% costs $510,178 in interest over 30 years, on top of the $400,000 itself. The total depends on two numbers: your rate and your loan size. A one point difference in rate changes the total by close to $100,000.
The number nobody shows you at closing
You sign a stack of papers at closing. Somewhere in there is the total you'll pay over the life of the loan. Most people never find it, and the people who find it don't believe it.
So here it is plainly. Borrow $400,000 at 6.5% for 30 years and pay exactly what the bank asks, every month, for 360 months. You will hand over $910,178. The house cost $400,000. The loan cost $510,178.
That isn't a trick or a fee. It's just interest, charged every month on whatever you still owe, for three decades. Your own total is on your loan documents, or a licensed agent can show it to you in a free payoff projection.
How much interest you'll pay at different rates
Here's the same $400,000, 30-year loan at six different rates:
| Rate | Monthly payment | Total interest over 30 years |
|---|---|---|
| 5.0% | $2,147 | $373,023 |
| 5.5% | $2,271 | $417,616 |
| 6.0% | $2,398 | $463,353 |
| 6.5% | $2,528 | $510,178 |
| 7.0% | $2,661 | $558,036 |
| 7.5% | $2,797 | $606,869 |
Notice how small the monthly differences look and how large the totals are. Going from 6% to 7% adds $263 a month. That feels manageable. Over 30 years, it adds about $94,700.
This is why shopping for a rate matters more than almost anything else in the mortgage process. Half a point, earned by improving your credit or comparing lenders, is often worth $45,000 or more.
How much interest you'll pay at different loan sizes
Now hold the rate at 6.5% and change the loan:
| Loan amount | Monthly payment | Total interest over 30 years |
|---|---|---|
| $250,000 | $1,580 | $318,861 |
| $350,000 | $2,212 | $446,406 |
| $400,000 | $2,528 | $510,178 |
| $500,000 | $3,160 | $637,722 |
| $600,000 | $3,792 | $765,267 |
A simple rule falls out of this table. At 6.5% over 30 years, you pay about $1.28 in interest for every $1 you borrow. Borrow $100,000 more and you're signing up for about $128,000 more in interest.
When the interest actually gets paid
Interest isn't spread evenly. It's front-loaded, which is the part that surprises people most.
Here's how the $400,000 loan at 6.5% plays out over time:
| After | Interest paid so far | Principal paid so far | Still owed |
|---|---|---|---|
| 5 years | $126,140 | $25,556 | $374,444 |
| 10 years | $242,497 | $60,895 | $339,105 |
| 15 years | $345,326 | $109,763 | $290,237 |
| 20 years | $429,446 | $177,339 | $222,661 |
Read the first row slowly. Five years of payments, about $151,700 sent to the bank, and the balance has dropped by only $25,556.
We call this the 85% problem. In the first year of a typical 30-year mortgage, about 85% of every payment goes to interest. We break down exactly why in our guide to how mortgage amortization works.
What a 15-year mortgage would have cost
For comparison, a $400,000 loan on a 15-year term at 6.0% has a payment of $3,375 and costs about $207,600 in total interest.
That's roughly $302,600 less than the 30-year loan at 6.5%. The catch is the payment, which is about $847 higher every month. Not everyone can carry that, and not everyone should. If you're weighing the switch, our guide to refinancing to a 15-year mortgage walks through when it makes sense.
How to pay less interest on the loan you already have
You can't change your rate without refinancing. But you can change how long the bank gets to charge it.
Every extra dollar that goes to principal stops being charged interest for the rest of the loan. That's why small extra payments do so much. On our $400,000 example, an extra $100 a month saves about $64,000, and an extra $200 a month saves about $112,000. Our guide to extra mortgage payments shows the full range.
For every strategy side by side, from biweekly payments to refinancing, see how to pay off your mortgage faster.
There's also a different approach. Instead of asking you to pay more, Ridgewell's Mortgage Accelerator Program is designed to change how your mortgage is structured so less of each dollar goes to interest. For qualifying households, it is designed to pay off a home in as little as 5 to 7 years.
Payoff timelines are illustrations for qualifying households and are not guaranteed.
Why the total matters
It's easy to treat the monthly payment as the only number that counts. That's what lenders quote and what budgets track.
But $510,178 is real money. It's money that could have gone toward retirement, a child's education, or simply a few years of not having a house payment at all. You don't have to pay it all. You just have to know it's there.
Where to start
Find your own total. Pull up your latest mortgage statement and note three things: your balance, your rate, and how many years you have left. Those three numbers decide what your loan will really cost.
Then get a free payoff projection from a licensed agent. It shows your current payoff date, the interest still ahead of you, and what's possible with your real numbers.
All examples assume 30-year fixed mortgages unless noted, principal and interest only, with figures rounded. Taxes, insurance, and PMI are not included.
