Work out student loan interest instantly with clear inputs, formula shown and shareable results.
Student loans typically accrue simple daily interest on the outstanding balance. Multiplying the daily accrual by days in the period shows exactly what a payment must beat before it starts reducing principal.
Daily accrual
Daily interest = Balance × annual rate / 365; Period interest = daily × days
Figures are estimates. Lenders apply their own rounding, fees and eligibility rules, and rates change. This is not financial advice — confirm the numbers with your lender.
Interest accrues every day, so paying earlier in the month means fewer days of accrual and more of the payment reaching principal.
Unpaid accrued interest being added to principal, after which it starts earning interest itself.