Student Loan Calculator
Monthly payment and total interest for federal or private student loans. Add extra principal to see how much sooner you'd be debt-free.
Results
Monthly payment
$0.00
Total interest
$0
Total paid
$0
Payoff in
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Standard repayment vs alternatives
This calculator uses the standard 10-year repayment plan — fixed monthly payment over a fixed term. Federal loans also offer income-driven plans (IDR), graduated payments, and extended terms that change the monthly payment but typically increase total interest.
Where extra payments help
Federal loans are simple-interest. Every extra dollar of principal saves you future interest on that dollar. The earlier the extra payment, the more it saves. A $100/mo extra on a $35k loan @ 5.5% over 10 years saves $2,880 in interest and shaves 31 months — about 2.6 years — off the term.
The formula
- M = monthly payment
- P = loan balance
- r = monthly interest rate (annual ÷ 12)
- n = total payments (years × 12)
Worked example
$35,000 balance, 5.5% rate, 10-year term, no extra payments:
- Monthly payment: $379.84
- Total interest over the term: $10,581.04
- Total paid: $45,581.04
Add $100/month extra toward principal and the payoff drops from 120 months to 89 — total interest falls to $7,700.56, a savings of $2,880.48, and you're done 31 months sooner.
Frequently asked questions
Does this handle income-driven repayment (IDR) plans?
No. IDR payments are based on your income and family size, not a fixed amortization schedule, and can be far below what's shown here — sometimes lower than the interest accruing, which grows the balance instead of paying it down. This calculator models the standard fixed 10-year plan only.
Do extra payments actually go to principal on federal loans?
Usually, but servicers differ in how they apply extra money by default — some spread it across all your loans, others put it toward the next payment due instead of principal. Log in to your servicer's site and explicitly direct extra payments to principal on the loan you're targeting.
Should I refinance federal loans with a private lender?
Refinancing can lower your rate, but it permanently converts federal loans into a private loan — forfeiting IDR eligibility, federal deferment/forbearance, and forgiveness programs like PSLF. It's worth considering mainly if you're confident you won't need those protections.
What happens to interest during forbearance or deferment?
On unsubsidized federal loans and virtually all private loans, interest keeps accruing during a pause and is typically capitalized — added to the principal — when payments resume. A pause makes the loan more expensive, not free, so it's worth using sparingly and paying accrued interest during the pause if you can.