How the Student Loan Forgiveness Calculator works
This calculator projects your loan balance forward, month by month, using the same compounding math behind any standard loan amortization schedule. Each month, interest accrues on the current balance, then your monthly payment is subtracted. That simulation runs for the length of your chosen forgiveness program — or stops early if the balance reaches zero first. Whatever balance remains when the term ends is the amount that would be forgiven.
The formula
For a starting balance B, a monthly interest rate r (annual rate ÷ 12), and a fixed monthly payment M, each month updates the balance as:
Balance = Balance × (1 + r) − M
This repeats for up to 120 months (10-year PSLF), 240 months (20-year IDR), or 300 months (25-year IDR), whichever program you select. If the balance reaches zero before the term ends, the calculator stops the simulation there and reports the payoff month instead of a forgiven amount.
Negative amortization
If your monthly payment is smaller than the interest accruing that month, the balance grows instead of shrinking — a pattern called negative amortization. This is common on income-driven repayment plans, where the required payment is based on a percentage of discretionary income rather than on what it would take to pay off the loan. The calculator models this automatically: there is no floor that stops the projected balance from rising above the original amount.
PSLF versus income-driven repayment forgiveness
- Public Service Loan Forgiveness (PSLF): forgives the remaining balance after 120 qualifying monthly payments — about 10 years — while working full-time for a qualifying government or nonprofit employer.
- Income-driven repayment (IDR) forgiveness: forgives the remaining balance after 20 years of qualifying payments on loans that only cover undergraduate study, or 25 years on loans that include any graduate study, regardless of employer.
Worked example
A $35,000 balance at 6% annual interest, paid down at $250/month under a 20-year (240-month) IDR term: the monthly rate is 0.06 / 12 = 0.5%. Because $250 sits just above the roughly $250.86 payment that would fully amortize this loan over 240 months, the balance shrinks steadily but does not quite reach zero — the projection lands around $347 remaining at month 240, which would be forgiven. Drop the payment to $150/month instead, and the interest accruing each month outpaces it: the balance grows to roughly $46,600 by month 240, all of which would be forgiven. Raise it to $300/month, and the loan pays itself off entirely around month 176, with nothing left to forgive.
What this calculator does not do
It does not determine your eligibility for any specific forgiveness program, apply real IDR payment formulas based on income and family size, or estimate taxes on a forgiven balance. Tax treatment of forgiven student debt depends on the program and the tax law in effect at the time of forgiveness, and has changed over time — confirm current rules with the IRS or a tax professional before relying on any number here for tax planning.