What this calculator does
Find out what your student loan payment will be each month, and how much the loan costs you in interest. This calculator works with a fixed-rate student loan. It shows the monthly payment and the interest that piles up before repayment begins. It also shows the total interest over the life of the loan and the month of your last payment. Add an extra monthly amount to see how much sooner the loan ends and how much interest that saves.
Most student loans don't need payments while you're in school, or for a short grace period after you leave. But on many loans, interest keeps building during that time. That interest is then repaid along with the amount you borrowed. So the amount you actually start repaying is larger than your original loan. The calculator shows both figures, so the jump isn't a surprise when your first bill arrives.
Where it's used
Why this math matters outside the classroom:
- Planning after graduation. A graduate with $30,000 at 6.52% over 10 years budgets about $352 a month once a 6-month grace period ends.
- Grace-period interest. Six months of simple interest on $30,000 at 6.52% is 30,000 × 0.0652 ÷ 12 × 6, which adds $978 to the amount owed.
- Comparing loan offers. Students compare a $10,000 loan at 5% and at 7% over 10 years, about $106 against $116 a month.
- Paying ahead. Borrowers check how an extra $100 a month on the default loan cuts almost three years off repayment.
- Family budgeting. Parents add an expected loan payment to a household budget to see how it fits beside rent and other bills.
Grade level and standards: Grades 11–12; Common Core State Standards for Mathematics HSA.SSE.B.4. © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.
How to use it
- Enter the loan balance and the interest rate. The default rate is the 2026–27 federal rate for undergraduate Direct Loans. Replace it with the rate on your own loan.
- Enter the repayment term in years or months. Then enter how many months of grace you have before payments start.
- Choose whether interest builds up during the grace period, or isn't charged, as with subsidized federal loans.
- If you like, add an extra monthly payment and the date the grace period begins. Then read the payment, total interest, payoff date and yearly table.
What the inputs mean
- Interest rate
- The fixed yearly rate on the loan. Federal rates are set each year for new loans, and stay fixed for the life of that loan. Private loans may be fixed or variable. The default of 6.52% is the federal undergraduate rate for loans first paid out from July 1, 2026 to June 30, 2027.
- Repayment term
- Ten years is a common standard term. Longer terms lower the payment but raise the total interest.
- Grace period before payments start
- The months after you leave school before your first payment is due. Six months is common on federal loans. Enter 0 if payments start right away.
- Interest during the grace period
- Unsubsidized and most private loans charge interest during the grace period. On subsidized federal loans, the government covers it. Check your loan type.
- Extra payment each month
- Any amount you pay on top of the required payment each month. It goes to principal (the amount you owe), so the required payment stays the same and the loan ends sooner.
- Grace period start date
- Usually the date you graduate or drop below half-time enrollment. The first payment is counted one month after the grace period ends.
Formula and method
grace interest = balance × rate ÷ 100 ÷ 12 × grace months amount repaid P = balance + grace interest i = rate ÷ 100 ÷ 12; n = term in months payment = P × i ÷ (1 − (1 + i)^(−n)); at 0%: payment = P ÷ n total interest = grace interest + payment × n − P with an extra payment: each month, balance = balance × (1 + i) − payment − extra
In the formulas, P is the amount you repay: what you borrowed plus any grace-period interest. i is the monthly interest rate, the yearly rate divided by 12. n is the number of monthly payments.
During the grace period, interest is simple. It's charged on the original balance each month, and it doesn't earn interest of its own. When it builds up, it becomes part of the amount you repay. That's how it raises the payment.
The payment comes from a standard loan formula. It finds the one fixed monthly amount that pays off the loan, with interest, in exactly n payments.
An extra payment is worked out month by month. Interest is charged on the balance. Then the required payment and the extra both bring it down. The loan ends in the month the balance reaches zero, with a smaller last payment.
Worked example
You owe $30,000 at 6.52% on a 10-year plan, with a 6-month grace period during which interest builds up.
- Grace-period interest: $30,000 × 6.52% ÷ 12 × 6 = $978.00.
- Amount repaid: $30,000 + $978 = $30,978.00.
- Monthly rate: 6.52% ÷ 12 ≈ 0.00543333; number of payments: 10 × 12 = 120.
- Payment: $30,978 × 0.00543333 ÷ (1 − 1.00543333^(−120)) ≈ $352.06.
- Total interest: $978.00 + $352.06 × 120 − $30,978.00 ≈ $12,247.71, so you repay about $42,247.71 in all.
- Paying $100 extra each month ends the loan after 86 payments (7 years 2 months) instead of 120. That saves about $3,392.87 in interest.
Result: The monthly payment is about $352.06, and the loan costs about $12,247.71 in interest. If the same loan were subsidized, so no grace-period interest built up, the payment would be about $340.95.
Understanding the result
The monthly payment is the number to plan your budget around. Compare it with your expected take-home pay. If the payment eats a large share of a starting salary, look at a longer term or a different plan.
Total interest shows the real cost of stretching the loan out. Longer terms make each payment smaller. But they keep the balance high for longer, so more interest builds up.
Even small extra payments shorten a loan noticeably. That's because every extra dollar lowers the balance that interest is charged on, for all the months that follow.
Assumptions and limitations
- One fixed-rate loan, repaid with equal monthly payments at the end of each month. Interest is the yearly rate ÷ 12, charged on the balance.
- Grace-period interest is simple interest on the original balance, and it's repaid with the loan.
- No interest builds up while you're still in school, before the grace period. Enter the balance as it stands when the grace period begins.
- Amounts aren't rounded to the cent. Lenders round, so their figures may differ by a few cents.
- It doesn't cover income-driven, graduated or extended plans. It also doesn't cover forgiveness programs, deferment or forbearance (pausing payments).
- Enter several loans with different rates one at a time. Or combine them using a weighted average rate as a rough guide.
- Federal rates and repayment rules change. This is an estimate, and your servicer's figures are the ones that count.
Frequently asked questions
Does interest really build up during the grace period?
On unsubsidized federal loans and most private loans, yes. On the default $30,000 loan at 6.52%, six months of grace adds $978 to the amount repaid. That raises the payment by about $11 a month. Paying that interest before repayment begins keeps the balance at its original amount.
How much does a longer term lower my payment?
Switch the term to compare. Stretching the default loan from 10 to 20 years lowers the payment. But interest runs for twice as long, so total interest more than doubles. Use the longer term only if you need the lower payment.
Is it better to pay extra or invest the money?
Paying extra earns a guaranteed return equal to the loan's rate, because every dollar of principal stops costing you that rate. Whether that beats investing depends on the returns you expect and how much risk you're comfortable with. The calculator shows the interest you'd save, so you can compare.
Why is the rate input labelled with a year?
Federal student loan rates are reset each year for new loans, based on a Treasury auction in May. Then they stay fixed for the life of each loan. The default shows the rate for loans first paid out in the 2026–27 award year. Loans from earlier years keep their own rates, so enter the rate printed on your loan.
Sources
- Federal Student Aid: Interest Rates for Federal Direct Loans First Disbursed Between July 1, 2026 and June 30, 2027 (GENERAL-26-33) (checked 2026-10-19)
How this calculator is checked
Method: Simple interest for the grace period; standard level-payment (annuity) formula with monthly rate = yearly rate ÷ 12 for repayment; month-by-month simulation for extra payments. The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.
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