See your payment, total interest, and how extra payments speed things up.
| Year | Interest paid | Remaining balance |
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A student loan amortizes the same way any fixed-payment loan does: each payment splits between interest and principal, and how much goes to each side shifts every month even though the total payment never changes.
Deferment and income-driven plans can let a student loan sit for years before the first payment is due, and interest keeps accruing that whole time. Repayment then starts against a balance that is often higher than the amount originally borrowed, so the interest owed on it is at its highest point right when payments begin. That gap closes the same way it does on any amortizing loan: as the balance drops, so does the interest calculated against it.
Yes. Extra payments go entirely to principal, and interest for every subsequent month is then charged on a smaller balance, so the saving compounds for the rest of the loan.
Timing changes the size of the effect. The same extra amount paid early, while the interest share of each payment is at its highest, cuts more total interest than it would later on. The extra payment field above reports the interest saved and how much sooner the loan clears.
Amortization means paying off a loan through equal periodic payments that combine interest and principal in shifting proportions. The payment amount stays fixed, but how much of it reduces your actual balance changes every month.
Early payments are mostly interest because interest is charged on whatever balance remains, and that balance is highest right after repayment starts. This is especially relevant for student loans, where deferment or income-driven plans can let interest accrue for years before repayment even begins, making the "early payments are mostly interest" effect even more pronounced than on other loan types.
The payment formula is: payment = P × [r(1+r)ⁿ] / [(1+r)ⁿ − 1], where P is the loan balance at the start of repayment, r is the monthly interest rate, and n is the number of scheduled payments. Extra payments made early, while the interest share of your payment is highest, reduce principal faster and cut more total interest than the same extra payment made later in the loan.