Student Loan Interest Calculator

Daily interest = Loan balance × (annual interest rate ÷ 365). Federal student loans use daily simple interest, so this amount accrues fresh every single day based on your current balance — it doesn't compound daily, but any unpaid accrued interest can be added to your principal (capitalized) at certain events, like leaving a grace period or exiting deferment.

Monthly interest ≈ Daily interest × number of days in that billing period (commonly approximated as 30.44 days, the average month length). Your exact monthly interest will vary slightly since months have 28-31 days.

If your payment is smaller than the interest that accrued since your last payment, the remaining unpaid interest keeps accruing (and can eventually capitalize into your principal) — this is common under income-driven repayment plans where the payment is based on income, not on covering the interest.

Yes — because interest accrues daily on your current balance, paying down principal earlier in the month (rather than waiting until the due date) reduces the balance interest accrues on for the remaining days, saving you a small amount of interest compared to paying on the last possible day.

This calculator divides by 365, the convention most federal loan servicers use (some use 365.25 to account for leap years, which produces daily interest about 0.07% lower — a negligible difference in practice). Your servicer's exact daily rate is shown on your loan statement if you want to match it precisely.