Student Loan Extra Payments Calculator with Extra Payments

The tool uses standard amortization formulas to compute scheduled payments and the effect of additional principal reductions. For recurring extras, the calculator increases the periodic payment and solves for the number of periods until balance reaches zero using the closed-form amortization inverse.

For one-time lump sums, the remaining balance just before the lump payment is computed, the lump sum is subtracted, and remaining periods are recomputed. Biweekly simulation assumes each biweekly payment equals half the monthly scheduled payment and uses the biweekly periodic rate (annual rate / 26).

Use recurring extras to reduce both payoff time and total interest; a lump sum early in the schedule yields larger interest savings than the same lump later.

This tool provides estimates only; always verify with your loan servicer for exact payoff amounts and to check for contractual limitations.

Example 1: $20,000 at 5% APR for 10 years. Adding $50/month reduces payoff time and saves interest — the calculator reports new payoff years and interest saved.

Example 2: Same loan, apply $1,000 at payment #6. The tool computes the balance at month 6, subtracts $1,000, then computes remaining payments.