Student Loan Amortization Calculator

All formulas use nominal annual interest rate (APR) converted into periodic rates by dividing by the number of periods per year. Monthly computations use 12 periods; biweekly computations use 26 periods. The standard annuity formula is used to compute level payments that amortize the loan over the stated term.

The accelerated biweekly mode models the typical consumer strategy of paying half the monthly payment every two weeks. This creates 26 half-payments per year (equivalent to 13 full payments), which effectively applies one extra monthly payment per year. Payoff time for that strategy is estimated by solving the annuity equation for the number of periods given a fixed per-period payment.

Accuracy and safety checks: the tool assumes payments are applied immediately and that the servicer compounds interest at the same periodic frequency. If a servicer applies interest daily or applies extra payments first to future payments instead of principal, results may differ. This tool does not replace official payoff quotes from your loan servicer.

Monthly amortization gives the baseline scheduled payment and total cost.

Biweekly annuity computes payments sized for 26 periods/year and the same term; amounts differ because period length differs.

Accelerated biweekly (half-monthly every two weeks) is modeled by fixing the biweekly payment to half the monthly payment and solving for the resulting payoff time; this typically reduces interest paid by creating effectively one extra monthly payment per year.

Example: $20,000 at 5.0% APR for 10 years. Standard monthly payment uses periods_per_year=12 and N=120. Accelerated biweekly using half-monthly payments uses payment = monthly_payment/2 and periods_per_year=26; solving for N shows a shorter payoff and lower total interest.

Example: If you enter an extra payment amount, the calculator treats it as an additional amount applied each scheduled payment period and re-estimates payoff time and total interest accordingly.