Student Loan Repayment Calculator
Calculate student loan payoff time, total interest paid, and total cost.
Enter your loan amount, interest rate, and monthly payment.
Student loan monthly payments are calculated using the standard amortization formula — the same math used for mortgages, auto loans, and any fixed installment loan.
Monthly Payment Formula:
M = P × [r(1+r)^n] / [(1+r)^n − 1]
- M = Monthly payment amount
- P = Principal (loan balance)
- r = Monthly interest rate (annual rate ÷ 12)
- n = Total number of payments (years × 12)
Worked example: Loan: $28,000 at 6.5% APR, standard 10-year repayment Monthly rate: 6.5% / 12 = 0.5417% = 0.005417 n = 10 × 12 = 120 payments M = 28,000 × [0.005417 × (1.005417)^120] / [(1.005417)^120 − 1] = 28,000 × [0.005417 × 1.9348] / [1.9348 − 1] = 28,000 × 0.01048 / 0.9348 = $314/month
Total paid: $314 × 120 = $37,680 Total interest: $37,680 − $28,000 = $9,680
Repayment plan comparison for $28,000 at 6.5%:
| Plan | Monthly | Total Interest |
|---|---|---|
| 10-year standard | $314 | $9,680 |
| 20-year extended | $209 | $22,160 |
| Income-driven (IDR) | Varies | Often more |
Key tips:
- Federal loans offer income-driven repayment — payments are capped at 10% of discretionary income
- Making one extra payment per year reduces a 10-year loan by roughly 14 months
- Refinancing to a lower rate only makes sense if you lose no federal protections you plan to use
- Interest begins accruing on unsubsidized loans during school — subsidized loans defer interest until graduation