Student Loan Calculator
Find your monthly student loan payment, total interest, and how much faster you pay off the loan — and how much interest you save — with extra monthly payments.
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Adjust the inputs on the left to see your monthly payment.
Federal student loans on the Standard Repayment Plan amortize over 120 months (10 years), while consolidation and many private loans stretch to 15, 20, or 25 years. This calculator computes the required monthly payment for your balance, rate, and term — then simulates what happens when you add an extra amount to every payment: how many months you shave off, and how much interest you never have to pay.
How it's calculated
Monthly rate r = APR ÷ 1200, n = term in months
Base payment M = P × r × (1 + r)^n ÷ ((1 + r)^n − 1)
With extra: each month, interest = balance × r
principal = (M + extra) − interest
repeat until balance = 0
For example, a $30,000 balance at 6.5% over 10 years requires $340.64 per month and costs about $10,877 in total interest. The extra-payment scenario is computed by month-by-month simulation rather than a closed-form formula, because the final payment is almost always a partial one.
Why extra payments are so effective: every extra dollar goes straight to principal, and student loan interest accrues daily on the outstanding principal. Shrinking the principal early in the loan eliminates all the future interest that principal would have generated. Federal student loans (and nearly all private ones) have no prepayment penalty, but you should tell your servicer in writing to apply overpayments to principal immediately rather than advancing your due date.
Assumptions and limitations: this tool models a single fixed-rate loan with monthly compounding. If you hold several loans at different rates, run them separately — and if you're choosing where to send extra money, the "avalanche" method (highest rate first) minimizes total interest. Income-driven repayment plans (IBR, and the plans that replaced SAVE under the 2025 reconciliation law) set payments from your income rather than amortization, so this calculator doesn't apply to them. Interest that capitalizes after deferment or forbearance should be included in the balance you enter.
Frequently asked questions
What is the standard repayment term for federal student loans?
The federal Standard Repayment Plan is 120 months (10 years). Direct Consolidation Loans can run 10–30 years depending on balance, and private lenders commonly offer 5-, 10-, 15-, and 20-year terms.
How much does an extra $100 per month actually help?
A lot. On a $30,000 loan at 6.5% over 10 years, paying $100 extra each month pays the loan off in 86 months instead of 120 — nearly 3 years early — and saves about $3,347 of interest. Use the extra-payment slider and watch the "Months to Payoff" and "Interest Saved" outputs update live.
Is there a penalty for paying off student loans early?
No. Federal student loans never carry prepayment penalties, and essentially all US private student loans are penalty-free too. Just instruct your servicer to apply extra amounts to principal, not to future payments.
Is student loan interest tax deductible?
Up to $2,500 of student loan interest per year is deductible as an above-the-line deduction (no itemizing required), subject to income phase-outs. Your servicer reports interest paid on Form 1098-E.
Does this calculator work for income-driven repayment plans?
No. Income-driven plans set your payment as a share of discretionary income rather than amortizing the balance over a fixed term. This calculator models standard fixed-payment repayment, which is how most private loans and the federal Standard Plan work.
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Results from this calculator are estimates for informational use only — not financial, medical, or professional advice. Read our full disclaimer before acting on any number you see here.