Cernarus

Student Loan APR Calculator with Extra Payments

This planner helps you compare the scheduled loan payment to adjusted schedules when you add recurring extra payments or apply a lump-sum to principal. It also provides a conservative APR estimate that annualizes upfront fees so you can compare offers on a like-for-like basis.

Results are estimates intended for planning. The tool uses standard amortization math and a conservative fee annualization method. It is not a substitute for the official APR disclosure from your lender or legal advice.

Updated Nov 15, 2025

Computes regular scheduled payment, applies optional recurring extra payments and a one-time lump-sum toward principal, and estimates payoff period and total interest paid.

Inputs

Results

Updates as you type

Scheduled payment (no extras)

$318.20

Payment including recurring extra

$318.20

Estimated periods to payoff (including lump-sum)

—

Estimated total interest paid

—

Estimated time saved

—

OutputValueUnit
Scheduled payment (no extras)$318.20—
Payment including recurring extra$318.20—
Estimated periods to payoff (including lump-sum)—periods
Estimated total interest paid——
Estimated time saved—years
Primary result$318.20

Visualization

Methodology

Scheduled payment is calculated from the standard amortization formula using the periodic rate r = annual_rate_pct / 100 / payments_per_year and number of periods n = term_years * payments_per_year.

Extra recurring payments are added to the scheduled payment and used to estimate an accelerated payoff period by solving the amortization equation for the number of periods. A one-time lump-sum is treated as an immediate principal reduction applied at the start of the schedule.

APR including fees is approximated by annualizing upfront fees (origination_fee ÷ principal ÷ term_years) and adding that percentage to the nominal annual rate. This is a conservative approximation for quick comparisons only; official APR calculations are lender-specific and may include additional finance charges.

Worked examples

Example 1: $30,000 at 5% for 10 years yields the scheduled monthly payment shown by the calculator. Adding $100 per month reduces payoff time and total interest; the time saved is reported in years.

Example 2: $20,000 at 6% for 15 years with a $500 origination fee produces an APR estimate that annualizes the fee on top of the nominal rate. Use this to compare offers that charge different upfront fees.

Further resources

Expert Q&A

Is the APR shown here the same as the lender's APR disclosure?

No. The APR estimate here is a conservative, quick method that annualizes upfront fees for comparison. Official APR disclosures from lenders may include additional finance charges and specific regulatory calculations. Use official lender disclosures for contractual purposes.

How accurate are the payoff and interest estimates?

Estimates use standard amortization math and assume constant interest and on-time payments. They do not model deferred interest, capitalization rules, changing rates, penalties, forbearance, or income-driven adjustments. Small numeric differences may occur due to rounding and floating-point arithmetic.

Why does the calculator sometimes show very large or invalid payoff periods?

If the recurring payment (including extras) is less than the interest that accrues each period, the balance will not decline and the formula cannot produce a valid payoff period. Increase your extra payment or shorten the payment frequency to produce a valid payoff estimate.

Should I rely on this tool for legal or tax decisions?

No. This tool is for informal planning only. Consult your lender, tax advisor, or legal counsel for actions that require legal, tax, or contractual certainty.

Sources & citations