Student Loan Repayment Calculator

Student loan payment calculations use standard loan amortization to determine the fixed monthly payment required to pay off the full balance — including all accrued interest — within the chosen repayment term.

Standard monthly payment formula: M = P × [r(1+r)^n] ÷ [(1+r)^n − 1]

Where:

• M = monthly payment
• P = total loan principal (sum of all disbursements)
• r = monthly interest rate = annual rate ÷ 12
• n = total repayment months (years × 12)

Total cost of loan: Total Paid = M × n

Total interest paid: Interest = Total Paid − P

What each variable means:

• Principal (P): the total borrowed amount. Include all loans if you have multiple.
• Annual Interest Rate: federal undergraduate subsidized loans: ~6.5% (2024). Graduate PLUS loans: ~8%. Private loans: 4–15%.
• Repayment Term: standard is 10 years (120 months). Extended plans stretch to 20–25 years (lower payments but far more interest paid).
• Grace Period: federal loans have a 6-month grace period after graduation. Unsubsidized loans accrue interest during this period, capitalizing at repayment start.

Federal repayment plan comparison ($35,000 at 6.5%):

• Standard 10-year: $397/month | Total interest: $12,600
• Extended 20-year: $261/month | Total interest: $27,640
• Extended 25-year: $236/month | Total interest: $35,800

Income-driven plans (IBR, PAYE, SAVE) base payments on income rather than loan balance — useful when income is low relative to debt.

Worked example: Loan balance: $45,000. Interest rate: 6.5%. Term: 10 years.

r = 6.5% ÷ 12 = 0.005417

M = 45,000 × [0.005417 × (1.005417)^120] ÷ [(1.005417)^120 − 1] = 45,000 × [0.005417 × 1.9563] ÷ [0.9563] = 45,000 × 0.011093 = $499.19/month

Total paid = $499.19 × 120 = $59,903 Total interest = $59,903 − $45,000 = $14,903

Refinancing to 4.5% with the same term saves approximately $5,200 in interest over 10 years — always compare refinancing offers if your credit score has improved since graduation.