Mortgage guide

How to pay off a 30-year mortgage in 15 years

By Sergio Ruiz · Last reviewed: October 9, 2026

The short answer

On a new $300,000, 30-year mortgage at 6.5%, paying an extra $718 a month (about $2,614 in total) finishes the loan in 15 years and saves about $212,344 in interest. The extra amount is roughly the gap between the payment on a 15-year loan and on a 30-year loan at the same rate.

How much extra do you need?

Each cell below shows the smallest whole-dollar extra payment per month that ends a new 30-year fixed-rate mortgage within 15 years, followed by the interest saved.

Loan amount	At 5.5%	At 6.5%	At 7.5%
$200,000	+$499 / $114,699	+$479 / $141,604	+$456 / $169,771
$300,000	+$748 / $171,999	+$718 / $212,344	+$684 / $254,657
$400,000	+$998 / $229,397	+$957 / $283,085	+$912 / $339,542

Each cell shows extra per month / interest saved. Extra amount applied to principal every month from the first payment. Method: How the calculator works.

Two patterns stand out. The extra amount grows in step with the size of the loan. And a higher rate needs a slightly smaller extra payment to reach 15 years, because the gap between the 15-year and 30-year payments narrows, while the interest you save is larger.

What if you cannot pay that much?

You do not have to reach 15 years to benefit. This table shows the $300,000 loan at 6.5%, whose scheduled payment is $1,896.20 and total interest is $382,633:

Extra per month	Total monthly payment	Interest saved	New payoff time
+$300	$2,196.20	$135,115	20 yr 10 mo
+$500	$2,396.20	$179,759	17 yr 6 mo
+$718	$2,614.20	$212,344	15 yr
+$800	$2,696.20	$221,926	14 yr 3 mo
+$1,000	$2,896.20	$241,162	12 yr 9 mo
+$1,300	$3,196.20	$262,477	11 yr

Assumptions: new $300,000 loan, 30-year fixed rate of 6.5%, extra amount applied to principal every month from the first payment.

Extra payments or a 15-year refinance?

On the same $300,000 at 6.5%, a true 15-year loan would have a payment of $2,613.32 and about $170,398 in total interest. Paying $718 extra on the 30-year loan costs $2,614.20 a month and about $170,289 in interest. At the same rate, the two roads cost almost the same. What differs is everything around the rate:

Flexibility. Extra payments are optional. If money gets tight you can go back to the scheduled payment. A 15-year loan makes the higher payment mandatory.
A new loan or your current one. A refinance replaces your mortgage with a new one: a new rate, a new term and new closing costs. Extra payments keep the loan you have.
The rate. If a 15-year loan would come with a lower rate than your current one, it can save more than the table shows. Compare both options with all costs included, not only the payment.

How to make it work

Start early. Interest is charged on the remaining balance, so extra money in the first years removes the most interest. See What happens if you pay an extra $200 a month.
Check for a prepayment penalty. The CFPB says penalties do not normally apply to small extra principal payments, but recommends confirming with your lender. See Prepayment penalty: what it is and how to check yours.
Designate it as principal. Ask your servicer how to mark an extra payment as principal-only, and confirm on your next statement that the balance dropped by the extra amount.
Keep a safety net. Money sent to a mortgage is hard to get back, so keep an emergency fund first, and consider paying off debt that costs more than your mortgage before you start.
Automate it. If a fixed extra amount is too much, start smaller and raise it when your income grows. Or try one extra payment a year.

Frequently asked questions

How much extra do I need to pay to finish a 30-year mortgage in 15 years?

On a new $300,000, 30-year mortgage at 6.5%, an extra $718 a month, for a total of about $2,614 a month, pays the loan off in 15 years and saves about $212,344 in interest. The amount depends on your loan size and rate.

Is paying extra the same as refinancing to a 15-year mortgage?

At the same interest rate, the monthly cost is almost identical. The difference is that a refinance replaces your loan with a new one, with a new rate and closing costs, and commits you to the higher payment, while extra payments keep your current loan and are optional.

Do I have to pay the extra amount every month?

No. Extra principal payments are voluntary unless your contract says otherwise, so you can pause or reduce them. The finish date moves back by the amount you skip.

Will I be charged a penalty for paying a mortgage off early?

Not necessarily. The CFPB says prepayment penalties do not normally apply if you pay extra principal in small chunks, but recommends confirming with your lender and reading your loan documents.

Related guides

Try your own numbers. Enter your balance, rate and remaining term, and test the extra amount that gets you to the date you want.

Open the calculator

Sources and method

All figures were calculated with the Financial Accelerator engine; the formulas and assumptions are public in How the calculator works. Other calculators can show slightly different results depending on when they credit the extra payment.
Consumer Financial Protection Bureau, What is a prepayment penalty? (reviewed September 11, 2024).

This page is educational and not financial, legal or tax advice. Rates and costs differ by lender. Confirm the terms of your own loan with your servicer.