About the Student Loan Calculator
Federal and private student loans both use standard amortization, but the terms and rates involved make a real difference in what you'll pay monthly and over the life of the loan. Our Student Loan Calculator projects your monthly payment and total cost from your balance, rate, and term.
How It Works
The calculator applies the standard fixed-rate loan payment formula to your total loan balance, interest rate, and repayment term in years, showing your monthly payment alongside total interest paid over the full life of the loan.
Formula & Methodology
Once you're in a standard, fixed-term repayment plan, a student loan amortizes exactly like any other fixed-rate installment loan - the interest rate and repayment term are the two levers that determine the trade-off between monthly payment and total lifetime cost. Extending the term to lower the monthly payment always increases total interest paid, since more months means more opportunities for interest to accrue on the outstanding balance.
Step-by-Step: Calculating It By Hand
- 1Convert the annual interest rate to a monthly rate.
- 2Convert the repayment term in years to total months.
- 3Apply the standard amortization formula to find the monthly payment.
- 4Multiply the monthly payment by the number of months and subtract the original balance to find total interest paid.
Examples
Standard 10-year term
A $30,000 balance at 5.5% over the standard 10-year federal repayment term comes to a monthly payment in the low $300s, with total interest adding several thousand dollars to the original balance.
Extended repayment term
The same balance on a 20-year extended repayment plan lowers the monthly payment significantly but roughly doubles the total interest paid over the life of the loan.
Advantages
- Works for both federal and private student loans using standard amortization
- Shows total interest cost, not just the monthly payment figure
- Useful for comparing standard versus extended repayment terms
- Helps set realistic budget expectations before or during repayment
Common Mistakes
- Not considering income-driven repayment plans, which change the payment formula entirely for federal loans
- Choosing an extended term purely for a lower payment without weighing the significantly higher total interest
- Forgetting that private student loans typically don't offer the same forgiveness or income-driven options as federal loans
- Not checking for any available interest rate reduction for enrolling in autopay
Edge Cases to Watch For
- Federal loans offer income-driven repayment plans that calculate payment as a percentage of discretionary income rather than fixed amortization, producing a completely different (and sometimes variable) monthly payment.
- Federal loan forgiveness programs (Public Service Loan Forgiveness and others) can make this standard-amortization total-cost comparison irrelevant for qualifying borrowers.
- Private student loans generally don't offer income-driven repayment or federal forgiveness programs, making standard amortization the primary repayment structure available.
- Interest may continue accruing during any deferment or forbearance period, adding to the balance before standard repayment even begins.
Common Use Cases
- Estimating monthly student loan payments before or during repayment
- Comparing standard versus extended repayment term trade-offs
- Budgeting for loan payments after graduation
- Understanding the total interest cost of a given repayment plan