Finance
Student Loan Repayment Calculator
Estimate a student-loan payment, total interest, and the effect of an extra monthly principal payment. The calculator uses payment = P × r ÷ (1 − (1 + r)^−n). It returns more than one result so you can check the main answer against a useful secondary measure. Extra principal usually lowers interest and term when the servicer applies it to the balance. Income-driven plans, subsidies, capitalization, forgiveness, and variable rates require program-specific modeling.
Educational scenario only. Confirm rates, fees, taxes, contract terms, and eligibility with the relevant institution or adviser.
Calculate and compare
Use the number box for precision or the slider for fast scenario testing.
Scenario results
Scheduled payment
$431.48
Before optional extra principal.
Payoff with extra
91 months
Modeled payoff duration.
Interest with extra
$10,194.35
Excludes entered monthly fees.
How the calculation works
Use consistent units and retain full precision until the final display step.
Worked example
Reproduce the displayed scenario, then change one assumption at a time.
Assumptions behind the result
- • Inputs use the units shown beside each control.
- • The displayed formula is applied without hidden market or demographic data.
- • Rounding occurs only for display; calculations keep full numeric precision.
- • Extra principal usually lowers interest and term when the servicer applies it to the balance.
- • Income-driven plans, subsidies, capitalization, forgiveness, and variable rates require program-specific modeling.
Mistakes that change the answer
- • Mixing percentages with decimals or mixing incompatible units.
- • Relying on a rounded intermediate value instead of the full result.
- • Changing several assumptions at once instead of testing loan balance separately.