How to Calculate

How to Calculate Student Loan Repayment

By Alex B.|Updated January 7, 2026|6 min read

For informational purposes only, not financial advice. Full disclaimer

The average student loan borrower graduates with about $33,000 in debt. On the standard 10-year repayment plan at 5.5% interest, that is a monthly payment of $358 and $9,894 in total interest — you pay back nearly $43,000 for $33,000 borrowed. Understanding how repayment calculations work helps you choose the right plan and find ways to pay less interest.

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As an investor in EdTech, I see the student debt problem from both sides. The math is clear: a $35,000 loan at 5.5% costs nearly $10,000 in interest over 10 years. I have watched graduates delay homeownership, retirement savings, and business ventures because of these payments. Understanding repayment options is not just financial planning; it is career planning.

Alex B.

Standard Repayment Calculation

M = P × [r(1+r)^n] / [(1+r)^n - 1]

Same formula as any fixed-rate loan. For $35,000 at 5.5% over 10 years (120 payments): monthly rate is 0.4583%, and the payment is $380/month. Total paid: $45,564. Total interest: $10,564. The standard plan has the lowest total cost because you pay the most each month, reducing the principal fastest.

Comparing Repayment Plans

For a $35,000 loan at 5.5%: Standard (10 years) costs $380/month, $10,564 total interest. Extended (25 years) costs $215/month but $29,575 total interest — nearly 3x the interest. Graduated starts at $220/month, rises to $660/month over 10 years, $12,130 total interest. Income-driven plans cap payments at 10-20% of discretionary income with forgiveness after 20-25 years.

The Power of Extra Payments

On a $35,000 loan at 5.5% (standard 10-year plan, $380/month): adding $100/month reduces payoff time from 10 years to 7 years and saves $3,100 in interest. Adding $200/month cuts it to 5.7 years and saves $4,900. Extra payments go entirely to principal, reducing the balance that accrues interest. Always specify that extra payments should be applied to principal, not advanced to the next month.

Example Calculation

You have $40,000 in student loans at 6% and want to compare paying minimum ($444/month for 10 years) vs. $600/month.

Standard payments: $444/month × 120 months = $53,289 total ($13,289 interest)
Accelerated at $600/month: payoff in 81 months (6.75 years)
Accelerated total: $600 × 81 = $48,600 ($8,600 interest)
Interest saved: $13,289 - $8,600 = $4,689
Time saved: 39 months (3.25 years)

Paying an extra $156/month saves $4,689 in interest and frees you from the loan 3+ years earlier.

Refinancing: When It Makes Sense

Refinancing replaces your current loans with a new loan at (hopefully) a lower rate. If you have $40,000 at 6% and can refinance to 4%, your 10-year payment drops from $444 to $405 and you save $4,729 in interest. Refinancing makes sense when: your credit score has improved since graduation, you have stable income, and you do not need federal loan protections (income-driven repayment, PSLF, forbearance).

Do NOT refinance federal loans if you are pursuing Public Service Loan Forgiveness (PSLF), are on or may need income-driven repayment, or are at risk of unemployment (federal loans offer forbearance; private loans often do not). Refinancing federal loans into a private loan permanently removes all federal borrower protections.

Target the Highest Rate First

If you have multiple student loans, make minimum payments on all and direct extra payments to the loan with the highest interest rate (avalanche method). This minimizes total interest paid. Once that loan is gone, roll its payment into the next highest rate loan.

Frequently Asked Questions

What is the standard student loan repayment term?+

The federal standard repayment plan is 10 years (120 payments) with a fixed monthly payment. Extended plans go up to 25 years with lower payments but much more total interest. Income-driven plans cap payments based on income with forgiveness after 20-25 years.

Should I refinance my student loans?+

Refinance if: your credit score is 700+, you have stable income, you can get a rate at least 1% lower, and you do not need federal protections (income-driven repayment, PSLF, forbearance). Do not refinance federal loans if there is any chance you will need these safety nets.

How much do extra payments save on student loans?+

On a $35,000 loan at 5.5%, an extra $100/month saves about $3,100 in interest and pays off the loan 3 years early. Even $50/month extra saves about $1,800 and shortens the loan by 1.5 years. Every extra dollar goes directly to principal reduction.

What is income-driven repayment?+

Income-driven plans cap your monthly payment at 10-20% of discretionary income. If your payment does not cover all the interest, the balance can grow (negative amortization). After 20-25 years of payments, the remaining balance is forgiven (though forgiven amounts may be taxable). These plans make sense for low earners with high debt.

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Disclaimer: This article is for informational purposes only and does not constitute financial advice. Consult a qualified financial advisor for decisions about your specific situation.