Free calculator · Personal Finance
Student Loan Payoff
Calculates the months to pay off a student loan and the total interest at the current monthly payment, then shows the time and interest an extra monthly amount could save. Inputs are the loan balance, the interest rate, the monthly payment, and the extra paid per month.
By Devon Coombs, CPA, MBA · Teaching Professor of Finance, Santa Clara University · Reviewed August 2026
Interactive Tool
Student Loan Payoff
At $350/mo
9 yr 11 mo
$9,567.17
total interest
At $450/mo
7 yr 3 mo
$6,813.28
total interest
Balance by month, with and without the extra
Interest saved
$2,753.89
by the extra $100/mo
Time saved
2 yr 8 mo
sooner to a zero balance
Each month: interest = balance × 5.5%/12, then the payment is applied; months are counted until the balance reaches $0
Extra payments generally save the most on the highest-rate loan first, and some income-driven federal plans change this math, so check the loan terms before committing.
Learn the concept
This calculator comes from the free Corporate Finance: The 10 Laws of Finance course, where the concept is taught with readings, worked examples, and practice questions.
Precomputed reference tables
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Built by Devon Coombs, CPA, MBA, Teaching Professor of Finance at Santa Clara University.