Student Loan Total Cost Calculator
See the total amount you'll pay over the life of a loan, and how much of that is interest, from your monthly payment, number of payments, and original loan balance.
Three lines, no interest rate required
total paid = monthly payment x number of payments
total interest = total paid - original balance
interest share = total interest / total paid x 100The rate is already baked into the payment your servicer bills, so the sum works from the statement in front of you. The defaults - $30,000 borrowed, $333.06 a month, 120 payments - come to $39,967.20 paid, $9,967.20 of it interest, and 24.9% of every dollar sent going to interest. Those figures happen to describe a 6% loan over ten years.
What the length of the loan does to the split
| Payment x count | Total paid | Interest share |
|---|---|---|
| $333.06 x 120 | $39,967 | 24.9% |
| $253.16 x 180 | $45,569 | 34.2% |
| $193.29 x 300 | $57,987 | 48.3% |
Same $30,000, same 6%, three repayment lengths. Stretched over twenty-five years almost half of every dollar you hand over is interest, and the total is nearly double what you borrowed. The share here is quoted against total paid; against the amount borrowed the first row reads 33.2% instead, which is how two sources describe one loan differently.
Frequently asked questions
How much will my student loan cost in total?
Your payment multiplied by the number of payments in the schedule - on the defaults, $39,967 to clear $30,000.
Why does it not ask for an interest rate?
Because it does not need one. The rate determined your payment; this works backwards from the payment itself, which makes it useful when you know what you are billed but not what rate produced it.
What share of my payments is interest?
24.9% on the default figures, rising to 48.3% over twenty-five years. Paying extra is what moves it: a smaller balance accrues less interest, so both the total and the share come down.