Student Loan Calculator
Updated · By the CalculatorDash editorial team · How we check our maths
Quick answer
A $35,000 student loan at 6.53% on a standard 10-year plan costs about $398 a month and about $12,750 in interest. Adding $100 a month pays it off about 31 months sooner and saves roughly $3,500 in interest.
How this calculator works
Most student loans are repaid like any other amortising loan: a fixed monthly payment over a set term. US federal loans default to a 10-year standard plan; longer plans lower the payment but raise the total interest.
Extra payments go straight to principal once interest is covered, so even a small amount each month shortens the loan noticeably. Make sure your servicer applies extra money to principal rather than advancing your next due date.
Income-driven repayment and forgiveness programmes follow different rules and aren't modelled here. If you work in public service or expect forgiveness, check those programmes before paying extra.
The formula
- Payment
- balance × r × (1 + r)^n ÷ ((1 + r)^n − 1)
- Months with extra
- −ln(1 − r × balance ÷ (payment + extra)) ÷ ln(1 + r)
- Interest saved
- standard interest − (months with extra × (payment + extra) − balance)
Worked example
A $35,000 balance at 6.53% over 10 years has a payment of about $398 and total interest of about $12,754. Paying $498 instead clears it in about 89 months rather than 120, with interest of about $9,231, saving roughly $3,520.
Tips
- 01Target extra payments at the highest-rate loan first.
- 02Ask about an autopay rate discount; many servicers offer 0.25%.
- 03Refinancing federal loans with a private lender can lower the rate but gives up federal protections.
Frequently asked questions
How is a student loan payment calculated?
For a standard plan, with the amortisation formula using the balance, monthly rate and number of months.
Is it worth paying extra on student loans?
If the rate is higher than what you can safely earn elsewhere and you have an emergency fund, extra payments are a guaranteed return equal to the interest rate.
Does this include income-driven repayment?
No. Income-driven plans base the payment on income and family size, and may forgive a balance later.
When does interest start on student loans?
It depends on the loan type. Subsidised federal loans don't accrue interest while you're in school; unsubsidised and private loans usually do.