Student Loan Repayment Calculator
Estimate your monthly payment, total interest, and amortization schedule for your student loan using the standard amortization formula.
Formula
Monthly Payment (M):
M = P × [r(1 + r)n] / [(1 + r)n − 1]
- P = Loan principal
- r = Monthly interest rate = Annual rate / 12
- n = Total number of monthly payments = Years × 12
Each month: Interest charge = Balance × r | Principal paid = Payment − Interest charge | New balance = Balance − Principal paid
Total Interest = Total Amount Paid − Principal
Assumptions & References
- Uses the standard fixed-rate amortization formula — the same method used by federal and private student loan servicers.
- Interest is compounded monthly (not daily); some lenders use daily compounding which may produce slightly different results.
- Extra payments are applied entirely to principal each month, reducing the balance faster.
- No origination fees, grace periods, or income-driven repayment adjustments are modeled.
- Federal student loan rates (2024–25): Undergraduate Direct Loans 6.53%, Graduate 8.08%, PLUS 9.08% — StudentAid.gov.
- Standard federal repayment term is 10 years; extended plans allow up to 25 years.
- Reference: CFPB Student Loan Repayment Guide.