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Student Loan Calculator

A student loan calculator estimates the standard monthly payment on a fixed-rate education loan. Add an optional extra monthly payment to see how much faster the loan is paid off and how much interest you save.

By the Personalloaned Editorial Team · Last updated 2026-09-16

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Method

How this calculator works

This calculator estimates the standard monthly payment on a fixed-rate student loan and shows what happens if you add a little extra each month.

Base payment: M = P * r * (1 + r)^n / ((1 + r)^n - 1).

With an extra amount E, the new payment is M + E and the payoff time becomes n = -ln(1 - r * P / (M + E)) / ln(1 + r).

  • P = amount borrowed
  • r = monthly rate = annual rate / 12 / 100
  • n = number of monthly payments

Extra payments go straight to principal, which cuts both the payoff time and the total interest. If the payment does not cover monthly interest, the balance never falls.

Use the rate and term from your own loan agreement; federal and private loans differ.

Common questions

Frequently asked questions

How do extra payments help?
Extra money reduces the principal faster, so less interest accrues each month. That shortens the payoff time and lowers the total interest paid.
Does this calculator cover income-driven repayment?
No. It models a fixed-rate loan with equal payments. Income-driven plans change the payment over time and need a different model.
What term should I use for a student loan?
Use the term stated in your loan agreement or the standard term you are considering. Terms vary, so enter the one that applies to you.
Why is my balance not falling?
If the payment is smaller than the monthly interest, none of it reduces the principal. In that case the calculator reports that the loan does not pay off.

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