Education is a good investment, and assuming some debt to earn a bachelor’s or advanced degree tends to pay off for most. For example, a student who took out the maximum direct student loan each year for four years would pay a little over $300 per month for 10 years to fully repay their loans. The average salary for a recent college graduate is over $51,000, and the Bureau of Labor Statistics shows median weekly earnings for bachelor’s degree holders being $461 higher than the median for those with only a high school diploma and unemployment rates 2% lower. So someone who borrowed the federal direct loan limit can reasonably expect to make up their loan payment every week just out of the salary differential.

That’s all well and good, but many Americans have much higher loan balances than that. Where does all that debt come from? The average loan balance upon graduation for the class of 2017 was over $39,000, and more than 2 million borrowers owe over $100,000 on their student loans. A large portion of those are people who attended graduate school, especially in medicine and law. And there are a number of borrowers who borrow larger amounts through private loan programs. But many find themselves with growing post-college loan balances due to deferrals or forbearance plans where interest accrues on the loan while nothing is being paid. Here’s how that works:

Let’s suppose you borrow the maximum direct student loan every year, and it’s completely unsubsidized (interest accrues on the full loan balance while you’re in school). Your $5,500 freshman year loan, at this year’s interest rate of 5.05%, would have a balance of $6,611 upon graduation. Calculating four years of loans, the $27,000 borrowed would have an added $3,232 in interest tacked on (at this year’s interest rate), bringing the loan balance up to $30,232. College graduates then have a 6-month grace period during which they’re not required to make payments. Doing so would add almost $700 to the loan balance, bringing it to $30,914. Even so, the monthly payment would remain in the low $300s range.

But what if that graduate went on to graduate school and continued deferring their loans for another two years? Sallie Mae’s Accrued Interest Calculator shows another $3,053 in interest accruing on the loan– $3,817 if the student takes advantage of the grace period following grad school– not to mention the likely scenario of additional borrowing to finance that additional education.

Forbearance makes sense in some circumstances, such as attending graduate school. However, a recently-released report shows that student loan servicers such as Navient are steering college graduates into forbearance when other repayment options such as income-driven plans might be better choices. Under an income-driven repayment plan, the borrower’s payment is capped at a factor of their income, recalculated annually. In some cases, when the payment is lower than the monthly interest on the loan, the additional interest may be subsidized by the federal government for up to 3 years. This means that the loan balance doesn’t grow as long as the borrower makes payments.

Limited borrowing to pay for college can make a lot of sense, but students and families need to be cognizant of the total borrowing over four years and what the loan balances will look like upon graduation. Then, it’s imperative to inform yourself about the repayment options before getting into one. This is especially true with interest rates rising and loan costs going up as a result.