Student Loan Payment Calculator

Calculations use standard amortization mathematics: periodic interest = annual APR divided by the number of periods per year. For monthly calculations the formula M = P*r/(1-(1+r)^-n) is used where r is the monthly rate and n the number of months. For period-based schedules the same annuity formula is applied with the period rate and period count.

The accelerated bi‑weekly option models making half the monthly amortizing payment every two weeks (26 payments/year). Because 26 half‑payments equal 13 full monthly payments per year, this accelerates principal reduction. The bi‑weekly amortization option computes a periodic payment that amortizes the loan exactly over term_years×26 periods.

Standards and good practice referenced: follow secure coding and data handling per NIST guidance for cryptographic and data protection controls; numeric accuracy and algorithm documentation principles align with ISO numerics and IEEE floating point recommendations; workplace and safety guidance cited from OSHA where relevant to application deployment. This tool is informational, not legal or financial advice.

Bi‑weekly accelerated (half monthly every two weeks) often reduces interest and shortens payoff relative to monthly payments because it results in one extra full monthly payment per year. True bi‑weekly amortization computes payments to fully amortize across 26×term years periods and may produce different per‑period amounts.

Use the calculator to compare methods with and without extra contributions. Consider rounding behavior and bank processing timing; actual results depend on your servicer's posting practices.

Example 1: $30,000 balance, 5.5% APR, 10 years remaining. Monthly schedule will produce a fixed monthly payment; accelerated bi‑weekly (half monthly every two weeks) typically yields an earlier payoff and lower total interest because of the extra annual payment equivalent.

Example 2: Adding a small extra amount to each bi‑weekly payment increases principal reduction and shortens payoff faster than the same extra split into monthly payments, because extra amounts are applied more frequently.