Student Loan Interest Accrual Calculator
Calculate simple daily interest from your principal, annual percentage rate and chosen day denominator.
Events: scenario name | YYYY-MM-DD | action (rate/principal/capitalize/payment) | value | interest allocation (payment only). Rate sets annual percent; principal adds a signed adjustment; capitalize transfers the entered amount from accrued interest to principal; payment subtracts explicit principal and interest allocations.
Date intervals include start and exclude end. Events act before that date’s accrual; same-date events follow input order. Actual-year mode splits at January 1 using 365/366 for the charged calendar year. Count mode requires your denominator and accepts no dated events. No automatic compounding, fees, legal rule, default rate or financial advice. Maximum 36600 charged days per scenario. Fees are not modeled; the total excludes fees and is principal plus accrued interest only. Events on the end date are recorded after the final charged day.
Exact fractions preserve full precision. Inputs stay in this browser. Maximum 30 scenarios, 100 event rows, 200 digits per decimal, 1000 result digits.
Report
A QUICK WALKTHROUGH
How to use this tool
- Enter principal, annual percent and day basis.
- Enter dates or a day count, then optional allocated events.
- Calculate the complete timeline and export the report.
Model and formulas
Each line: name | principal | annual rate (%) | day denominator (positive integer or actual) | start (YYYY-MM-DD or whole day count) | end (YYYY-MM-DD; blank for day count) | currency label. Events: scenario name | YYYY-MM-DD | action (rate/principal/capitalize/payment) | value | interest allocation (payment only). Rate sets annual percent; principal adds a signed adjustment; capitalize transfers the entered amount from accrued interest to principal; payment subtracts explicit principal and interest allocations. Date intervals include start and exclude end. Events act before that date’s accrual; same-date events follow input order. Actual-year mode splits at January 1 using 365/366 for the charged calendar year. Count mode requires your denominator and accepts no dated events. No automatic compounding, fees, legal rule, default rate or financial advice. Maximum 36600 charged days per scenario. Fees are not modeled; the total excludes fees and is principal plus accrued interest only. Events on the end date are recorded after the final charged day.
Report
Exact fractions preserve full precision. Inputs stay in this browser. Maximum 30 scenarios, 100 event rows, 200 digits per decimal, 1000 result digits.
GOOD TO KNOW
Common questions
Can this determine my contractual balance?
No. The result follows only the supplied daily model and events; check your loan terms separately.