Free online estimator — see exactly how much interest you'll pay
This free student loan interest calculator shows you exactly how much interest you'll pay over the life of your student loans. Many borrowers are shocked to learn that interest can add tens of thousands of dollars to the total cost of their education. This tool makes it easy to see the real cost of your student debt.
Enter your loan principal balance, interest rate, and repayment term to see your monthly payment and total interest cost. You can also add extra monthly payments to see how much interest you'd save by paying off your loan faster.
Federal student loans accrue interest daily using the simple daily interest formula. Your daily interest rate is your annual rate divided by 365. Each day, interest is added to your principal balance (capitalized) when you enter repayment.
During your grace period or deferment, unsubsidized loans continue to accrue interest. When you enter repayment, that unpaid interest gets added to your principal balance — meaning you'll pay interest on interest.
How is student loan interest calculated?
Federal student loans use simple daily interest. Your annual interest rate divided by 365 gives you the daily rate. Each day, interest accrues on your current principal balance. When you make a payment, it first covers accrued interest, then reduces principal.
What's the average student loan interest rate?
Current federal student loan rates range from about 5-7% for undergraduate loans, 6-8% for graduate loans, and 7-10% for Parent PLUS loans. Private student loans vary more widely, from 4-15% depending on credit.
Does paying extra monthly really save that much on interest?
Absolutely. For a $35,000 loan at 5.5% over 10 years, paying an extra $100/month saves you about $3,500 in interest and pays off the loan 2 years early. Small extra payments make a huge difference over time.
What's the difference between subsidized and unsubsidized loans?
Subsidized loans don't accrue interest while you're in school or during deferment — the government pays it for you. Unsubsidized loans start accruing interest immediately, even while you're in school. This calculator works for both types.
Does this calculator work for private student loans too?
Yes! The math is the same for both federal and private student loans. Just enter your private loan balance and interest rate, and it'll calculate the same way.
Federal student loans use **simple daily interest**, which means interest accrues every single day on your current principal balance. Here's the math:
When you make a payment, it first covers the interest that's accrued since your last payment. The rest goes toward reducing your principal. This is why paying extra toward principal is so powerful — you're cutting out future interest charges.
Not all student loans are created equal. Here's the breakdown:
Tired of making student loan payments? Here are proven strategies to pay them off early and save thousands in interest:
How much interest do I pay on a $35,000 student loan?
On a $35,000 student loan at 5.5% over 10 years, you'll pay about $10,400 in total interest. That means your total repayment is $45,400 — you're paying back 30% more than you borrowed. If you pay extra each month, you can cut that interest significantly.
Does student loan interest capitalize?
Yes — and it's expensive. Capitalization happens when unpaid interest gets added to your principal balance. After that, you're paying interest on the new, higher principal (which includes the old unpaid interest). This is called "interest on interest" and it can add tens of thousands to your total cost. That's why it's smart to pay interest while you're in school if you can afford it.
What's the current student loan interest rate?
As of 2026, federal student loan rates are: ~5.5% for undergrads, ~7% for grad students, ~8% for Parent PLUS loans. Rates reset every July based on the 10-year Treasury note. Private student loan rates vary much more (4-15%) depending on your credit and the lender.
Is it better to pay off student loans early or invest?
It depends on your interest rate. If your student loan rate is 6-7%, paying them off early is like getting a guaranteed 6-7% return on your money — hard to beat. If your rate is 3-4%, you might be better off investing in the stock market (which averages 7-10% annually). A common strategy: pay off high-interest loans first, then invest.
Can I deduct student loan interest on my taxes?
Yes! You can deduct up to $2,500 in student loan interest each year on your federal taxes. It's an "above-the-line" deduction, so you don't even need to itemize. There are income limits (phases out around $75,000-$90,000 for single filers). Keep track of your interest payments — your servicer sends you a 1098-E form each year.