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.

Small extra payments compound fast. Making just one extra monthly payment per year (effectively a 13th payment) shaves about 14 months off a standard 10-year loan and saves roughly 10% of total interest. The reason: every extra dollar paid against principal early reduces every future month’s interest charge. Smaller, consistent extra payments often outperform a single large lump sum applied later.

Subsidized vs unsubsidized — a critical distinction during school.

• Subsidized federal loans (Direct Subsidized, for undergraduates with demonstrated financial need): the government pays the interest while you’re in school at least half-time, for 6 months after, and during deferment. No interest accrues during these periods.
• Unsubsidized federal loans (Direct Unsubsidized, available to most students): interest accrues from the day the loan is disbursed, including during school. If you don’t pay the interest as it accrues, it capitalizes (adds to principal) at the end of the grace period. A $25,000 unsubsidized loan at 6.5% can capitalize an extra $3,200+ in interest before you make your first payment.
• Private loans: almost always unsubsidized, often capitalize interest aggressively, and may require in-school payments.

The single best move for unsubsidized borrowers still in school: pay the interest each month from a part-time job or summer earnings. Even $50 a month prevents capitalization and saves thousands long-term.