Student Loan Daily Interest Calculator
Estimate daily simple interest and the interest accrued over a selected number of days. Choose the day-count convention explicitly instead of hiding it in the math.
Calculator for daily simple interest and accrued student loan interest under a selected day-count convention.
Inputs and day-count assumption
$
Use principal only, excluding unpaid accrued interest unless it has capitalized.
Enter the annual rate shown for the loan.
Enter a whole number of calendar days for this estimate.
The divisor applies to both the displayed daily rate and accrued-interest estimate.
Your results
Estimated interest over the entered days
$122.05
Over 30 days using a 365-day divisor.
Calculation detail
Estimated interest per day
$4.07
Daily interest rate: 0.015068%
This uses simple interest on the entered principal and does not model capitalization, payments, rate changes, subsidies, or servicer posting cutoffs.
Official federal materials use both 365 and 365.25 in different contexts. The selected convention stays visible so the estimate is reproducible.
The Daily Interest Formula
Daily interest equals principal × annual rate ÷ the selected day-count divisor. Accrued interest equals that full-precision daily amount × the entered days. The calculator rounds only the displayed dollar totals, not each day before multiplying.
StudentAid.gov illustrates the estimate with 365 days. Some federal servicer materials use 365.25, so this tool offers both and labels the choice.
Why a Statement May Differ
The estimate assumes the principal and rate stay constant for the entire interval. It does not reproduce capitalization, payment posting, rate changes, subsidies, or account-specific corrections. Use a servicer payoff statement for an amount due on a specific date.
Daily Student Loan Interest FAQs
StudentAid.gov presents a 365-day estimate, while some federal servicing materials describe 365.25. Use the convention relevant to the statement or servicer calculation you are checking and keep it identified when comparing results.
Federal student loan interest generally accrues as daily simple interest on principal. Unpaid interest may capitalize in specified circumstances, after which interest accrues on the higher principal balance.
Not necessarily. A payoff statement can reflect a different day-count convention, posting date, capitalization event, payment allocation, subsidy, or other account-level adjustment.