Choose repayment, extra payments or an in-school projection
A student loan raises three different questions, so this page has three calculators. The repayment tab solves one unknown from the other three: the monthly payment, the loan balance, the interest rate or the time to repay. The extra payments tab compares your required payment with a plan that adds extra money each month, once a year or once at a time you choose. The in-school tab projects what happens before repayment starts, when you may still be borrowing and interest may be building up.
Pick the tab by where you are. If you are already repaying a loan and want to know the payment or the payoff date, use repayment. If you want to know what an extra payment would save, use extra payments. If you are still studying or about to borrow, use in school and enter each payout with its month. All three use the same monthly accrual: each month the lender adds one twelfth of the annual rate to the balance, and your payment goes to that interest first. The currency selector changes labels only, and nothing you enter leaves your browser.
If you are unsure which tab you need, start with repayment. It is the fastest way to see a payment for a balance you know, and solving for a different unknown, such as the payoff time at a payment you choose, takes one change to the selector. Move to extra payments when your bill fixes the payment and you are considering paying more, and to the in-school tab when part of the loan has not yet been paid out.
Payment formula and how extra repayments change the schedule
Inputs and units
Enter the balance, the nominal annual rate and the number of monthly payments. The monthly rate is the annual rate divided by 12, i, and the level payment is balance × i ÷ (1 - (1 + i)^(-n)), or balance ÷ n at a 0% rate. For 30,000 at 6% over 120 months the payment is 333.06 and the total interest is 9,967.38. Raise the rate to 6.8% and the payment becomes 345.24 with 11,428.92 of interest. To find the payoff time, enter a payment and leave the term open: 30,000 at 6.8% with 350 a month is repaid in 9 years and 10 months, with a smaller final payment of 238.54.
Timing and assumptions
Extra payments work on the same schedule, applied after each month's interest. With 30,000 at 6.8% and a required 350 a month, the loan lasts 9 years and 10 months and costs 11,188.54 in interest. Adding 150 a month shortens that to 6 years and 2 months and 6,767.26, saving 4,421.28 of interest and 3 years and 8 months. The regular payment stays the same; the calculator does not assume your lender recalculates it. A yearly extra is paid in months 12, 24 and so on, and a one-time extra in the month you name. If several extras fall in one month they are added together once.
Boundary cases
If the payment does not cover the first month of interest, the balance never falls, so there is no payoff date and the calculator says so. At 0% interest the payment is simply the balance divided by the months: 12,000 over 12 months is 1,000.00. If the rate you solve for would be below 0% or above 100%, or the loan would take more than 1,200 months, the result is withheld with a message instead of a guess. Balances and payments accept up to two decimals and must be above 0.
Simple accrued interest, loan tranches and capitalization
Before repayment, a student often borrows in stages, and interest depends on when each amount is paid out. The in-school tab lets you add each payout as a tranche with an amount and the month it arrives, together with any principal you already owe. A tranche is added at the start of its month, before that month's interest, so money borrowed in month 7 is not charged for months 1 to 6. Interest accrues simply: each month it equals the principal times the annual rate divided by 12, and it is tracked separately from the principal.
You choose two things that decide what happens next. First, whether you pay the interest during school. If you do, it is an out-of-pocket cost each month and nothing builds up. If you do not, the interest accrues unpaid. Second, what happens to unpaid interest when repayment starts. It can stay separate, which means repayment pays it down first and it never earns further interest, or it can be capitalized, which means it is added to the principal once, when repayment begins, and interest is then charged on the larger balance. These are your assumptions, not a statement of a federal or lender rule; loan contracts differ, and you can also enter a range of months in which no interest accrues if your terms say so.
With 10,000 borrowed at 6% and 12 months to graduation, unpaid interest is 600.00. If that is capitalized, repayment starts on 10,600.00; if it stays separate, the principal is 10,000.00 and 600.00 of interest is owed in addition, so the total owed is the same on the first day but the later interest differs. A 10,000 tranche paid out in month 7 instead builds only 300.00 of interest by month 12. The comparison table puts paying interest now beside letting it build, with the cost out of pocket during school shown separately so that early payments are not treated as free.
Worked student-loan examples
Enter these inputs
For repayment, enter 30,000, 6% and 120 payments and find the payment. For extra payments, enter a 30,000 balance, 6.8% and a required 350 payment, with 150 extra every month. For in school, enter 10,000 already borrowed, 12 months to graduation, no grace period, a 6% rate and a 120-month repayment term, with interest not paid during school.
Read the output
The payment is 333.06 a month. Extra payments cut 3 years and 8 months and 4,421.28 of interest. For the in-school example, paying the 600.00 of interest during school costs that much out of pocket and repayment starts at 10,000.00; not paying it leaves 10,600.00 owed at the start, a monthly payment of 117.52 against 111.02, and a lifetime cost of 14,102.38 against 13,922.46.
Change one assumption
Switch the unpaid interest to capitalized and the starting balance becomes 10,600.00. Mark months 1 to 6 as interest-free and unpaid interest falls to 300.00. For a wider view of your debts, compare a wider debt repayment plan, or compare another debt payment obligation.
Smaller or irregular extras still help. A 1,000 payment once a year, perhaps from a tax refund or a bonus, shortens the loan with a 350 required payment by 2 years and 4 months and saves 2,702.06 of interest. A single 5,000 payment in month 6 saves 3,773.01 and 2 years and 1 month. Earlier extra payments save more interest than later ones of the same size, because they reduce the balance that interest is charged on for longer.
Model limits and where to confirm your loan terms
This is a monthly-accrual model. It does not calculate income-driven repayment, forgiveness or eligibility, and it does not include fees. A servicer may accrue interest daily, apply payments in a different order, treat dates differently or change terms after an event such as a consolidation. Results can therefore differ from your statement, and your statement is the authority. For federal loans in the United States, use the official studentaid.gov tools for current plan and eligibility rules; elsewhere, use the information from your lender or your government's student finance service.
Use the calculator to compare choices and see the size of the effect: how much a payment changes with a longer term, how much interest an extra payment saves, how much interest builds during school. Then confirm the real figures with your loan documents before you act.
Before acting on any result, gather four facts from your servicer: the current principal balance, the interest rate on each loan, whether interest is capitalized and when, and the required payment. Borrowers often hold several loans with different rates; enter them one at a time or, for a rough view, use a weighted average rate. Also check how your servicer applies an extra payment, whether to the highest-rate loan, to the next due payment or to principal, because that decides how much it really saves. This calculator assumes the extra money goes to this loan's principal after the month's interest.
Student loan questions
Will this calculate income-driven repayment or forgiveness?
No. Use the official current program tools for eligibility and repayment-plan rules.
Does unpaid interest always compound in school?
This model tracks it separately until the capitalization event you choose; actual contract rules vary.
Can I enter several loan disbursements?
Yes. Assign a month and an amount to each tranche so later borrowing is not charged interest too early.
Why can the result differ from a servicer?
Daily accrual, actual dates, fees, payment allocation and contract events may differ from monthly assumptions.
Do extra payments lower the required payment?
The comparison holds the regular payment fixed and estimates an earlier payoff; it does not assume your lender recasts the loan.