Student loan interest accrual is the daily charge your lender adds to your account based on what you currently owe. On federal loans, the math is simple: your outstanding principal times your annual interest rate, divided by the number of days in the year. That daily amount attaches to your balance every day, including weekends and holidays, and it keeps running whether or not you’re required to make a payment. The reason accrual matters more than the daily number suggests is capitalization: at certain moments, the unpaid interest gets folded into your principal, and from then on you pay interest on that interest too.
How the Daily Charge Is Calculated
Federal loans use simple daily interest. Your servicer takes your current principal, multiplies by your annual rate, and divides by the days in the year. Most servicers use 365.25 to account for leap years; some use 365.
A worked example makes the mechanics concrete. On a $30,000 balance at 6.39%, the annual interest is $30,000 × 0.0639 = $1,917. Divided by 365.25, that’s about $5.25 a day. That $5.25 accrues every day the balance sits there. Pay the principal down and the daily charge shrinks. Let unpaid interest capitalize into the principal and the daily charge grows.
Federal rates are fixed for the life of the loan and are set annually using a formula tied to the 10-year Treasury note yield plus a statutory add-on that varies by loan type.1Federal Student Aid. Interest Rates for Direct Loans First Disbursed Between July 1, 2025 and June 30, 2026 Once your loan is disbursed, its rate doesn’t change.
When Interest Starts Building, by Loan Type
Not every federal loan starts costing you on day one, and the distinction shapes how much you owe by the time you enter repayment.
Direct Subsidized Loans
The government pays the interest on subsidized loans while you’re enrolled at least half-time, during the six-month grace period after you leave school, and during eligible deferment periods.2Federal Student Aid. Top 4 Questions: Direct Subsidized Loans vs. Direct Unsubsidized Loans Your balance stays flat through those windows. Interest becomes yours to pay once you enter active repayment or a period of forbearance.
Direct Unsubsidized Loans and PLUS Loans
Interest starts accruing the day the funds are disbursed to your school. There are no exceptions.2Federal Student Aid. Top 4 Questions: Direct Subsidized Loans vs. Direct Unsubsidized Loans Time in class counts. The grace period counts. Deferment counts. Borrow $20,000 in unsubsidized loans at 6.39%, spend four years in school without paying anything, and roughly $5,112 in interest will be waiting for you at graduation. It won’t sit there quietly. When you enter repayment, it capitalizes.
Forbearance
Forbearance is the boundary case worth calling out. Interest accrues on every federal loan during forbearance, including subsidized loans. Borrowers who assume their subsidized loans stay interest-free during hardship pauses are often surprised. Forbearance has its uses in a real emergency, but on the interest side it’s one of the more expensive ways to stop payments.
What Capitalization Is and When It Happens
Before capitalization, accrued interest sits as a separate line on your account. After capitalization, it becomes part of the principal that generates new daily interest. That’s where accrual quietly turns into a larger bill than borrowers expect.
Federal regulations authorize the Department of Education to capitalize unpaid accrued interest at specific moments.3eCFR. 34 CFR 685.202 – Charges for Which Direct Loan Program Borrowers Are Responsible The common triggers:
- Entering repayment after the grace period, for interest that accrued on unsubsidized loans during school and grace.
- Exiting deferment, for unsubsidized and PLUS loans.4eCFR. 34 CFR 685.202 – Charges for Which Direct Loan Program Borrowers Are Responsible – Section: Capitalization
- Exiting forbearance, for all unpaid interest that built up while payments were paused.
- Missing the annual income recertification deadline on an income-driven plan, which resets your payment to the standard amount and may capitalize unpaid interest.5Federal Student Aid. Income-Driven Repayment Plans
Back to the earlier example. That $30,000 balance with $2,000 of accrued interest becomes a $32,000 principal after capitalization. At 6.39%, the daily charge moves from about $5.25 to about $5.60. Thirty-five cents a day sounds trivial, but stretched over a 20-year repayment period it adds thousands to what you finish paying. Each capitalization event resets the principal upward permanently, and every day of accrual after that runs on the higher number.
How to Keep Accrual From Ballooning
The most effective response is also the simplest: pay accrued interest before a capitalization event locks it in. You don’t have to wait for repayment to begin. During school, during the grace period, and during deferment, you can make voluntary payments that cover just the interest.6MOHELA. Borrower In Grace Even a partial interest payment shrinks the pile that eventually capitalizes.
On $20,000 of unsubsidized loans at 6.39%, the monthly interest is roughly $106. Paying that each month during school keeps the balance at $20,000 instead of letting it drift toward $25,000 by graduation. If $106 a month isn’t realistic, $50 still cuts the capitalization amount nearly in half. Many borrowers don’t know these payments are an option, and servicers don’t usually go out of their way to mention it.
If you’re on an income-driven repayment plan, recertification discipline matters. Missing the deadline doesn’t just recalculate your monthly payment; it can capitalize the unpaid interest that had been building.5Federal Student Aid. Income-Driven Repayment Plans Mark the recertification date yourself and submit early. Servicer reminders help, but relying on them alone is a gamble with real dollars attached.
How Consolidation Affects Your Interest
A Direct Consolidation Loan combines multiple federal loans into one, with a new fixed rate calculated as the weighted average of the underlying rates, rounded up to the nearest one-eighth of one percent.7Federal Student Aid. 5 Things to Know Before Consolidating Federal Student Loans That rounding means the consolidation rate will almost always sit slightly above the true weighted average.
There’s a second effect that catches people off guard. Any outstanding accrued interest on your existing loans capitalizes into the new principal balance before the weighted average rate is applied. If you’ve spent years in school with substantial accrued interest on unsubsidized loans, consolidating locks that interest into principal permanently. The rate calculation also uses your loans’ official rates and ignores any rate reductions you may already be receiving, such as auto-pay discounts.7Federal Student Aid. 5 Things to Know Before Consolidating Federal Student Loans Consolidation can simplify your monthly logistics. It rarely saves money on interest.
Private Loans Work Differently
The rules above cover federal loans. Private lenders aren’t bound by the federal program, and the mechanics of accrual can shift in ways that matter. Federal loans always use simple daily interest, but private loans may use simple or compound interest depending on the lender and the promissory note. With compounding, accrued interest folds into principal on a set schedule, sometimes daily or monthly, throughout the life of the loan. That’s ongoing, automatic capitalization built into the loan’s structure.
Private loan rates are also frequently variable, tied to a benchmark like SOFR or the Prime Rate plus a margin based on your credit. A variable rate means the daily charge can move month to month as the index moves. Federal law requires lenders to disclose the APR, the interest rate, and other key terms before you sign, but the specific compounding schedule lives in your promissory note. On a six-figure balance over 10 or 15 years, daily versus monthly compounding is a meaningful difference.
Private loans also carry no interest subsidy. Interest accrues from disbursement, and no government program covers it during school or hardship. If you hold both federal and private loans, that’s usually the argument for aiming extra payments at the private balance first.