The cost of federal student loans will soon be pricier.

The government sets annual interest rates on student loans once a year. The percentage is based on the 10-year Treasury note, which has been on the rise, including recently hitting 3 percent.

The bump was higher than expected this year, said Mark Kantrowitz, a student loan expert.

"How investors feel about the economy has an impact on what the rates are, and there's a lot of chaos going on," Kantrowitz said, pointing to talk of tariffs and President Donald Trump's announcement that the U.S. is pulling out of the Iran nuclear deal.

"It just happens to be bad timing from the point of view of the interest rates on student loans," he said.

Here's what borrowers need to know:

The interest rate on new undergraduate loans will rise to 5.05 percent for the 2018-2019 academic year, up from 4.45 percent last year.

For graduate students, loans will come with a 6.6 percent interest rate, compared with 6 percent now.

Plus loans for graduate students and parents will have a 7.6 percent interest rate, an increase from 7 percent.

All federal education loans issued after July 1, 2018, will be subject to the new rates.

Don't worry about loans you've taken out for previous academic years: Federal student loan rates are fixed, and the rates on those existing loans won't change.

(Sorry, families: You can't try to evade the rate increase by borrowing ahead of that deadline. Loans for the 2018-19 academic year must be taken out after July 1.)

Still, just half of students and parents know that students aren't guaranteed the same interest rate on the federal student loans they borrow each year, according to a recent report by online loan marketplace Credible.com.

"People go back each year and the rate can change," said Stephen Dash, CEO at Credible. "People should be particularly aware of that given the rising interest rate environment."

The rate changes apply only to federal student loans. Private loans come with their own — often higher — interest rates.

Borrowers can use Kantrowitz's calculator on his website PrivateStudentLoans.Guru to plug in their loan details and learn what they'll wind up owing.

Credible.com also has a handy loan cruncher, that will provide you a clear breakdown of how much you'll pay back in principle and interest.

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