Student Loan Calculator
Calculate student-loan payment, payoff time, total interest and savings from optional extra monthly payments.
- Shows standard payment and accelerated payoff
- Simulates extra principal month by month
- Reports total interest and estimated interest saved
Calculator workspace
Change any assumption and recalculate. Your entries stay in this browser unless you choose to share or copy a result.
What this Student Loan Calculator calculates
Student-loan decisions are often more useful when the payment and the total cost are shown together. This calculator first computes the normal fixed monthly payment for the entered balance, annual rate, and repayment term. It then adds any extra monthly amount and runs a month-by-month payoff simulation. That means the displayed payoff time and interest savings are based on the changing balance rather than a simple proportional estimate.
The result is intentionally more than a single number. Supporting figures are shown beside the headline answer so you can see which part of the calculation is driving the outcome. This makes the tool useful for scenario testing: change one assumption, calculate again, and compare the supporting values rather than relying on a black-box result.
Formula and calculation method
Required payment uses fixed-rate amortization; optional extra principal is simulated each month against the declining balance.
Inputs are validated before calculation and the arithmetic runs locally in the browser. Monetary fields use the selected currency only for display formatting. The calculator does not retrieve bank, payroll, property, medical, market or exchange-rate data from an external service.
How to use it
- Enter values that describe the same scenario and reporting period.
- Keep percentages and units consistent with the labels shown beside each input.
- Select Calculate and review both the headline result and the supporting metrics.
- Change one assumption at a time to understand sensitivity instead of accepting a single scenario.
- Use Copy Result, Share Result or Save Result Image when you need to keep a record of the calculation.
Worked example
For a 35,000 balance at 6.8% over ten years, calculate the normal payment first. Then enter an extra 100 per month. The result compares the original ten-year interest cost with the accelerated schedule and shows how many months the additional principal may remove from the repayment period.
How to interpret the result
An extra payment can have a disproportionate effect when it is applied directly to principal early in repayment. Before relying on the savings estimate, confirm how your loan servicer applies extra payments and whether any special program, subsidy, forgiveness path, or income-driven repayment arrangement would make early payoff undesirable.
For an important decision, compare the output with original documents, lender or employer terms, supplier information, professional guidance, or other authoritative records relevant to the calculation. Small differences in rates, timing, fees and definitions can materially change a result even when the formula itself is correct.
Important assumptions and limitations
This is a fixed-rate amortization model. It does not model variable rates, capitalization events, deferment, forbearance, income-driven repayment, forgiveness, tax consequences, subsidies, or multiple loans with different rates. If you have several loans, calculate them individually or use a debt-payoff tool that can rank balances and rates.
This calculator is for planning, checking, education and general informational use. It is designed to make assumptions visible and calculations reproducible, but it does not replace a contract, disclosure, professional opinion, medical assessment, accounting policy or lending decision.
Frequently asked questions
Does the extra payment reduce principal?
The calculator assumes the extra amount is applied to principal after monthly interest is charged.
Can I use it for private and federal loans?
Mathematically yes for a fixed-rate balance, but program rules and borrower protections can differ.
Why can payoff time differ from a lender statement?
Daily interest conventions, payment timing, fees, capitalization and servicer rules can create small differences.