How much interest will I pay on $30,000 in student loans?

On the standard 10-year plan at 6.52 percent, $10,913.92, for $40,913.92 paid in total. A fixed $400 a month cuts the interest to $8,637.69. Stretching the same loan to 25 years raises the interest to $30,881.17.

How is student loan interest calculated each month?

Interest equals the balance times the APR divided by 12, in the monthly approximation used here. Federal loans accrue interest daily at the APR divided by 365, which lands within a few dollars of the monthly figure on a stable balance.

Does student loan interest accrue while I am in school?

On unsubsidized loans, yes, from the day the loan is disbursed. A borrower who takes $5,500 a year for four years accrues $3,586.00 of interest before repayment starts, and the balance at repayment is $25,586.00 on $22,000 borrowed. Subsidized loans do not accrue interest while the borrower is in school at least half time.

Is student loan interest tax deductible?

Up to $2,500 a year, for borrowers whose modified adjusted gross income is below the phase-out, and it can be taken without itemizing. The deduction softens the cost by the borrower's marginal rate, but it does not make the interest free.

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The graduation ledger · Table No. 42

How Much Interest Will I Pay on My Student Loan?

Interest is a monthly charge on the balance you still owe, and the term decides the total more than the rate does. This article prices the interest by balance, rate, and term, and counts the interest that accrues before repayment even starts.

Filed October 30, 2026 · figures checked against 2026 sources

Interest is a monthly charge on the balance you still owe

Student loan interest is simple to state and easy to underestimate. Each month, the loan charges the balance times the APR divided by 12. At 6.52 percent, that is about 0.54 percent of the balance every month. A $30,000 balance costs $163.00 in interest in the first month. Whatever part of the payment is left after the interest reduces the balance, and next month's interest is a little lower. That is the whole mechanism, and it is worth working through slowly, because the monthly framing hides the ten-year cost. Half a percent a month sounds small. It is $1,956 a year on a $30,000 balance that never moves, and a balance that never moves is exactly what a payment below the interest produces. The APR is a yearly rate, but it is collected monthly, on a balance that the payment is only slowly reducing, which is why the total interest over a payoff is always much larger than one year of interest at the APR.

In practice, federal loans accrue interest daily, using a daily rate equal to the APR divided by 365, on the outstanding principal balance. The calculator on this site uses the monthly approximation, balance times APR divided by 12, which lands within a few dollars of a real servicer statement on a stable balance and matches the independently published $10,000 example to the dollar. The daily method matters most when the balance moves a lot during a billing cycle, because payments change the balance day by day. It matters least when the balance is stable and no new disbursements are added, which is the repayment scenario this series models. The grace period is the other daily-method fact worth knowing: after leaving school, a borrower gets six months before repayment begins, but interest accrues during the grace period on unsubsidized loans, and it capitalizes, which means it is added to the principal, when repayment starts. The balance at repayment is therefore larger than the amount borrowed, and the interest total is computed on the larger number.

How much interest, by balance, rate, and term

The table below is the answer to the title question, computed by this site's calculator on the standard 10-year plan. Read a row as the full price of borrowing that amount at that rate for ten years. At $30,000 and the 6.52 percent undergraduate rate, the interest is $10,913.92, which is 36 percent of the amount borrowed. At $100,000, it is $36,379.72. At the graduate rate of 8.07 percent, a $30,000 loan costs $13,811.20 in interest, and at the PLUS rate of 9.07 percent it costs $15,739.77. The cheapest cell in the table, $10,000 at 6.52 percent, still costs $3,637.97, which is the figure the published example for the same inputs gives, to the dollar, and which is the check that the model matches the real amortization rather than a simplified version of it.

Balance	Rate	Monthly payment	Interest over 10 years	Total paid
$10,000	6.52%	$113.65	$3,637.97	$13,637.97
$30,000	5.00%	$318.20	$8,183.59	$38,183.59
$30,000	6.52%	$340.95	$10,913.92	$40,913.92
$30,000	8.07%	$365.09	$13,811.20	$43,811.20
$30,000	9.07%	$381.16	$15,739.77	$45,739.77
$50,000	6.52%	$568.25	$18,189.86	$68,189.86
$100,000	6.52%	$1,136.50	$36,379.72	$136,379.72

The rate rows are the ones to study, because they show how much of the interest total is the rate and how much is the term. Moving from the 6.52 percent undergraduate rate to the 9.07 percent PLUS rate on the same $30,000 adds $4,825.85 of interest and $40.21 a month. Moving from the 6.52 percent rate to a hypothetical 5 percent saves $2,730.33. But the term rows, below, dwarf the rate rows. The same $30,000 at 6.52 percent costs $10,913.92 over ten years, $17,099.19 over fifteen years at $261.66 a month, $23,766.08 over twenty years at $224.03 a month, and $30,881.17 over twenty-five years at $202.94 a month. Stretching the term from ten years to twenty-five saves $138.01 a month and costs $19,967.25 more in interest, which is nearly double the ten-year interest total. The monthly saving is real, and in a tight month it is the right trade, but it is worth knowing that the trade is priced at almost twenty thousand dollars.

Term	Monthly payment	Interest	Total paid
10 years	$340.95	$10,913.92	$40,913.92
15 years	$261.66	$17,099.19	$47,099.19
20 years	$224.03	$23,766.08	$53,766.08
25 years	$202.94	$30,881.17	$60,881.17

The interest that accrues before repayment starts

Unsubsidized federal loans accrue interest from the day they are disbursed, including while the borrower is in school, and the interest that accrues before repayment is added to the principal when repayment begins. The numbers are larger than most borrowers expect. A borrower who takes $5,500 a year for four years, all unsubsidized at 6.52 percent, accrues $358.60 of interest on the first year's loan in its first year, and by the time repayment starts, the four years of loans have accrued $3,586.00 of interest in total: $1,434.40 on the first year's loan, $1,075.80 on the second, $717.20 on the third, and $358.60 on the fourth. The balance at repayment is $25,586.00 on $22,000 borrowed, which is 16 percent more than the amount borrowed, before a single payment has been made. Subsidized loans do not accrue interest while the borrower is in school at least half time, which is why they are the better loan when the borrower qualifies, and why the distinction between subsidized and unsubsidized is worth more than the interest rate difference between them. Paying the interest while in school, even $30 a month, stops the capitalization entirely, and it is the cheapest interest a borrower will ever pay, because it is paid before it starts earning interest of its own.

The new insight

Interest is charged on time, not just on money. The $30,000 loan at 6.52 percent costs $10,913.92 over ten years and $30,881.17 over twenty-five, a difference of $19,967.25 for the same balance at the same rate, and the only thing that changed is the number of months the balance exists. Every month added to a repayment is a month of interest on the remaining balance, so the term is the interest rate in disguise: the 25-year plan behaves like a much higher rate than the one printed on the loan, because it buys the lender fifteen more years of interest. Cutting the months is cutting the interest, dollar for dollar, with no negotiation required, and the cheapest month to cut is always the first one, because its interest saving compounds for the whole remaining term.

What changes the interest total, in order of effect

First, shorten the term. Moving from the standard 10-year plan to a fixed $400 payment cuts the interest from $10,913.92 to $8,637.69, a saving of $2,276.23, and moving to $500 cuts it to $6,404.75, saving $4,509.17. Second, do not stretch the term to lower the payment unless the month requires it, because the 25-year plan's $138.01 a month of relief costs $19,967.25. Third, pay the interest while in school on unsubsidized loans, which stops $3,586.00 of capitalization on a typical four-year borrowing pattern. Fourth, check the rate: a graduate borrower at 8.07 percent pays $2,897.28 more interest than an undergraduate borrower at 6.52 percent on the same $30,000, and refinancing into a private loan at a lower rate can cut the interest, but only by giving up the federal protections, the income-driven plans, and any forgiveness, which is a trade that should be priced in full before it is made. Fifth, pay extra in months when there is slack, because every extra dollar reduces every subsequent month's interest charge. The order matters: the term first, the rate second, and the in-school interest throughout.

Interest, taxes, and the fine print that is not fine print

Student loan interest is deductible in the United States, up to $2,500 a year, for borrowers whose modified adjusted gross income is below the phase-out, which begins at $75,000 for single filers in recent years, and the deduction is an adjustment to income, which means it can be taken without itemizing. That softens the cost by the borrower's marginal rate: $1,891.02 of first-year interest at the defaults is worth about $416 in tax saved for a borrower in the 22 percent bracket, though the exact figure depends on the phase-out and the filing status. The deduction does not make the interest free. It makes it cheaper, by roughly a fifth, for the borrowers who qualify. The fine print that matters more is the capitalization rule: interest that accrues during deferment, forbearance, and the grace period on unsubsidized loans is added to the principal when the period ends, and from then on it earns interest itself, which is how a balance can grow during a period when no payment is due. Forbearance is not free. It is a pause that the balance pays for, at the loan's rate, for the whole length of the pause.

Sources

Federal Student Aid, on 2026-27 Direct loan interest rates (undergraduate 6.52 percent, graduate 8.07 percent, PLUS 9.07 percent), on daily interest accrual and capitalization, and on the student loan interest deduction as administered by the Internal Revenue Service. Education Data Initiative, on average borrowing patterns. All interest figures were computed month by month by this site's calculator under the stated model, and the $10,000 at 6.52 percent standard payment of $113.65 a month, with $3,637.97 of interest, matches the independently published figure of about $113.64 a month and about $3,637 of interest.