What This Calculator Tells You
Enter your loan balance, interest rate, and the monthly payment you can make, and this tool solves the amortization equation for the two numbers that matter: how many months until the balance hits zero, and how much interest you'll hand over along the way. It works for a single federal loan, a private loan, or a consolidated balance — anything that charges a fixed rate and takes level monthly payments. Because it solves for the term from your real payment, you can also test what happens when you pay more or less than the standard amount.
A Worked Example
Say you graduate with $30,000 in unsubsidized loans at a 6.5% fixed rate on the standard 10-year plan. The monthly payment works out to about $341, and over 120 payments you'll pay roughly $10,900 in interest — meaning the degree's loan costs about $40,900 in total. Bump the payment to $391 (an extra $50) and you finish in about 100 months with around $8,900 in interest, keeping roughly $2,000 in your pocket. Those two scenarios are one field change apart in the calculator above.
Standard, Extra, or Refinance
The standard 10-year plan retires the loan fastest and cheapest, which is why federal loans default to it. Extra payments push the payoff date earlier because every added dollar skips the interest line and reduces principal directly. Refinancing swaps the whole loan for a lower rate — attractive if you have strong credit and steady income, but it converts federal loans to private and forfeits income-driven plans and forgiveness. Run each version here and compare the interest totals side by side before you decide.
Student Loan Repayment Calculator
How to Use This Calculator
- Enter Your Loan Balance: Use the current principal balance from your servicer's statement, not the original amount borrowed. If interest has capitalized on an unsubsidized loan, that higher figure is your real starting balance.
- Enter Your Interest Rate: Type your loan's APR — federal undergraduate loans are commonly in the 5-7% range, graduate and private loans often higher. Use the exact rate from your statement for an accurate term.
- Enter Your Monthly Payment: Enter what you actually pay each month. To test extra payments, add $25 or $50 to the standard amount and watch the payoff months drop.
- Click Calculate: The tool solves the amortization formula and returns your months to payoff, total interest, and total amount paid instantly in your browser.
- Compare Scenarios: Change the payment or rate and calculate again. Line up the interest totals to see exactly what an extra payment or a refinance would save you.
How It Works
Student loans amortize the same way a mortgage does: each monthly payment covers that month's interest first, and whatever is left chips away at the principal. Early on, most of your payment is interest; near the end, almost all of it goes to principal.
The basic rule:
- Months to Payoff — n = -ln(1 - Balance × r / Payment) / ln(1 + r) — This solves the amortization formula for the number of payments, where r is the monthly rate (APR ÷ 12). If your payment doesn't exceed one month's interest — Balance × r — the loan never pays off and the term is undefined.
The result assumes a fixed rate and equal payments. Federal loans and most private loans use simple daily interest, so paying a few days early or late shifts the totals slightly from this estimate.
Tips & Considerations
- If your payment is less than one month's interest (Balance × APR ÷ 12), the balance grows instead of shrinks and the loan never pays off — raise the payment above that threshold first.
- Extra payments help most in the first few years, when the interest portion of each payment is largest; the same $50 saves more applied in year one than in year eight.
- Tell your servicer to apply extra money to principal, not to prepay next month's bill — otherwise it won't shorten your term.
- On unsubsidized loans, paying even just the interest during school or deferment stops it from capitalizing and inflating your starting balance.
- Before refinancing federal loans, weigh the interest savings against losing income-driven plans, deferment, and forgiveness — run both rates here to see the actual dollar gap.
Frequently Asked Questions
How much does paying extra each month actually save?
A lot, because every extra dollar goes straight to principal and stops accruing interest for the rest of the term. On a $30,000 balance at 6.5%, the standard payment is about $341/month, finishing in 120 months with roughly $10,900 in interest. Add $50/month and you pay it off in about 100 months and cut interest to around $8,900 — saving roughly $2,000 and 20 months.
Standard 10-year plan vs. an income-driven plan — which costs less?
The standard plan (fixed payments over 120 months) almost always costs the least total interest because you pay the loan down fastest. Income-driven plans (like SAVE or IBR) lower the monthly payment by stretching the term to 20-25 years, so you pay far more interest over time — sometimes double. Choose income-driven when you need the lower payment to afford your budget, not to save money.
Should I refinance my student loans?
Refinancing replaces your loans with a new private loan at a lower rate. Dropping a $40,000 balance from 7% to 5% saves roughly $3,000-$4,000 in interest over 10 years. The catch: refinancing federal loans into a private loan permanently gives up income-driven plans, deferment, and any forgiveness. Only refinance federal debt if you have stable income and won't need those protections.
What's the difference between subsidized and unsubsidized loans?
On subsidized federal loans, the government pays the interest while you're in school and during deferment, so the balance doesn't grow until repayment begins. Unsubsidized loans accrue interest the entire time — if you don't pay it during school, that unpaid interest capitalizes (gets added to principal) at repayment, and you then pay interest on interest. Pay down unsubsidized interest early if you can.
How long does it take to pay off student loans?
The federal standard plan is 10 years, or 120 months. This calculator works backward from your actual payment: enter your balance, rate, and monthly payment and it solves for the exact number of months. If you pay more than the standard amount, the term shrinks; if you pay only the minimum on a stretched plan, it can run 20-25 years.
Why does my loan barely shrink in the first year?
Amortization front-loads interest. On that $30,000 loan at 6.5%, the first $341 payment includes about $163 of interest, so only ~$178 reduces the balance. As principal drops, the interest portion shrinks and more of each payment attacks the balance — which is exactly why extra payments early in the loan save the most.