Student Loan Interest Accrual Calculator
Calculate how interest accrues daily and monthly on your student loan, and see the total interest paid over the full repayment period.
Formulas Used
Daily Interest Accrual:
Daily Interest = Principal × (APR / 365)
Monthly Interest Accrual:
Monthly Interest = Principal × (APR / 12)
Standard Monthly Payment (Amortization):
M = P × [r(1+r)n] / [(1+r)n − 1]
where P = principal, r = monthly interest rate (APR/12), n = number of months
Total Interest Paid:
Total Interest = (M × n) − P (adjusted for actual payoff month)
Daily Rate:
rdaily = APR / 365 — the U.S. Department of Education uses a 365-day year for federal loans.
Assumptions & References
- Reference: U.S. Department of Education — How Interest Is Calculated (studentaid.gov); Truth in Lending Act (Regulation Z), 12 CFR Part 1026.