Student Loan Calculator
It shows the standard payment on a student loan and what an extra amount each month does to the payoff date and the total interest paid.
Standard monthly payment
$444.08
Standard payment
$444.08
Standard term
10y 0m
Standard interest
$13,290
With extra
$644.08
New payoff
6y 3m
Interest saved
$5,274
$5,274 saved, 3y 9m earlier
Paying $200.00 extra each month adds $15,000 of payments but removes $5,274 of interest.
Tell your servicer in writing to apply overpayments to principal — many will otherwise treat the money as paying next month's instalment early, which saves nothing.
What it calculates
It shows the standard payment on a student loan and what an extra amount each month does to the payoff date and the total interest paid.
Why it matters
Extra payments go straight to principal, so their effect compounds. A modest amount each month can remove years from a loan and thousands from its cost.
Who it's for
Graduates on a standard repayment plan, and anyone deciding between paying a loan down faster and investing the same money.
Formula
- B
- Current loan balance
- r
- Monthly interest rate
- n
- Number of payments in the standard term
- X
- Extra amount paid each month
Worked example
$40,000 at 6% over 10 years, plus $200 a month
- 1Standard payment = $444.08 a month
- 2Standard interest over 120 months = $13,289.84
- 3At $644.08 a month the loan clears in 75 months
45 months and $5,273.70 of interest saved
How the student loan calculator works
Each payment covers the interest accrued that month first, and only what remains reduces the balance. Because an extra payment faces no interest charge of its own, every additional dollar comes straight off principal — and that principal then stops generating interest for the whole remaining term. The effect is why the interest saved is far larger than the total extra paid. Federal loans have no prepayment penalty, so the only question is whether the guaranteed return equal to your interest rate beats the alternative use of that money.
Each payment covers the interest accrued that month first, and only what remains reduces the balance. An extra payment faces no interest charge of its own, so every additional dollar comes straight off principal.
That principal then stops generating interest for the entire remaining term, which is why the interest saved is far larger than the total extra paid.
Common mistakes
- Not telling the servicer to apply extra payments to principal, so they sit as a prepaid future instalment.
- Paying down a low-rate subsidized loan ahead of higher-rate debt.
- Refinancing federal loans privately without considering the protections that are lost.
- Assuming interest capitalization has not already increased the balance during deferment.
Tips and best practice
- State explicitly that extra payments go to principal, and check the next statement.
- Target the highest interest rate first when you hold several loans.
- Compare the loan rate against your expected investment return before choosing to prepay.
Frequently asked questions
How much can I save by paying extra on student loans?
On $40,000 at 6% over ten years, an extra $200 a month clears the loan 45 months early and saves about $5,274 in interest.
Should I pay off student loans early or invest?
Paying down the loan is a guaranteed return equal to the interest rate. Investing may beat it but is not guaranteed, so the loan rate is the benchmark.
Is there a penalty for paying off student loans early?
Federal student loans have no prepayment penalty, and neither do most private ones. Check your specific agreement if it is a private loan.
How do I make sure extra payments reduce the principal?
Instruct the servicer in writing to apply overpayments to principal. Otherwise many will treat the money as paying next month's instalment early.
What is the standard repayment term?
Ten years for most federal loans. Longer terms lower the monthly payment but increase the total interest substantially.
Related calculators
Methodology & trust
- Formula source
- Standard amortization applied to US federal student loan repayment terms
- Last updated
- 2026-07-28
- Privacy
- Every calculation runs in your browser. No inputs are sent to a server or stored.