How to Calculate What You'll Pay Each Month on Student Loans
How to estimate your monthly student loan payment
Your monthly payment depends on three things: how much you borrowed, what interest rate you're paying, and how long you have to repay. If you know those three numbers, you can calculate your payment yourself using a simple formula, or you can use an online calculator that does the math for you. The payment will be different if you're on an income-driven repayment plan instead of the standard 10-year plan — those plans tie your payment to what you earn, not to a fixed amount.
Before you estimate, gather your loan documents or log into your loan servicer's website. You'll need your loan balance, interest rate, and the repayment term you're considering. If you have multiple loans, you'll calculate each one separately, then add them together.
Key Takeaways
- Your monthly payment is determined by your loan balance, interest rate, and repayment term — the longer the term, the lower the monthly payment but the more interest you pay overall.
- Federal student loans offer income-driven repayment plans that calculate your payment as a percentage of your discretionary income, which may be lower than the standard 10-year payment.
- You can estimate your payment using an online calculator, a spreadsheet formula, or by contacting your loan servicer directly for an exact figure.
- Private student loans typically use only the standard repayment formula and do not offer income-based payment options.
The standard repayment formula
The standard repayment plan for federal loans runs 10 years. The formula that calculates your monthly payment is the same one banks use for car loans and mortgages. If you have a loan balance of $30,000 at 5% interest over 10 years, your monthly payment would be approximately $283. If you stretch that same loan over 20 years, your payment drops to about $159 per month — but you pay roughly $8,000 more in interest over the life of the loan.
The formula itself is: M = P × [r(1 + r)^n] / [(1 + r)^n − 1], where M is your monthly payment, P is the principal (amount borrowed), r is your monthly interest rate (annual rate divided by 12), and n is the total number of payments. You don't need to do this by hand — a calculator does it faster and without error.
Using an online calculator
The U.S. Department of Education offers a free loan payment calculator on StudentAid.gov. You enter your loan balance, interest rate, and how many years you want to repay over, and it shows you the monthly payment and total interest paid. Private loan servicers often have their own calculators on their websites too. These tools are faster than doing the math yourself and they show you how changing the term changes your payment.
When you use a calculator, try different scenarios. See what your payment would be over 10 years, 15 years, and 20 years. See what happens if you pay extra each month. This helps you understand the trade-off between a lower monthly payment and paying more interest overall.
Income-driven repayment plans for federal loans
Federal student loans offer four income-driven repayment plans: SAVE, PAYE, REPAYE, and IBR. On these plans, your monthly payment is calculated as a percentage of your discretionary income — the difference between your gross income and 150% of the federal poverty line for your family size. Your payment could be as low as $0 per month if your income is below the poverty line, or it could be higher than the standard payment if you earn a high income.
SAVE is the newest plan and generally offers the lowest payments. On SAVE, your payment is 5% of your discretionary income if you're a recent graduate, or 10% if you're not. The other plans use 10% to 20% depending on which one you choose. To estimate your payment on an income-driven plan, you need your most recent tax return or your current year's expected income. The Federal Student Aid website has a tool that estimates your payment under each plan so you can compare them.
Income-driven plans also offer loan forgiveness after 20 to 25 years of payments, depending on the plan. This means if you still owe money after that time, the remaining balance is forgiven — though you may owe income tax on the forgiven amount. This makes income-driven plans worth considering even if the monthly payment is higher, because the forgiveness benefit changes the total cost of the loan.
What affects your payment estimate
Your interest rate is locked in when you take out the loan and doesn't change. Federal student loans have fixed rates set by Congress. Private loans may have fixed or variable rates — variable rates can go up or down, which changes your payment if you're on a variable-rate loan. When you estimate, use the rate you actually have, not an average rate.
Your loan balance is what you borrowed plus any interest that has accrued and been added to the principal. If you've been in school and haven't started repaying yet, interest may have been building up. Check your loan servicer's website to see your current balance — it's not the same as what you originally borrowed.
The repayment term you choose is the only thing you control after the loan is made. A shorter term means higher monthly payments but less interest paid overall. A longer term spreads the cost across more months but costs more in total interest. There's no single "right" choice — it depends on your budget and how much total interest you're willing to pay.
Comparing federal and private loan payments
Federal loans use the standard formula or an income-driven plan. Private loans use only the standard formula — they don't offer income-based payments. This is a major difference. If your income is low or unstable, federal loans are usually better because you can lower your payment through an income-driven plan. If your income is high and stable, the difference between federal and private payments may be smaller.
Private loans also have higher average interest rates than federal loans, though rates vary by lender and your credit score. When you estimate a private loan payment, use the actual rate your lender quoted you, not an average. The payment will be higher than a federal loan at the same balance and term if the interest rate is higher.
What to do after you estimate
Once you have an estimate, check it against your budget. Can you afford that payment? If not, consider a longer repayment term or, for federal loans, an income-driven plan. If you can afford more, paying extra each month reduces how much interest you pay and shortens how long you're in debt.
Contact your loan servicer to confirm your estimate is correct. Servicers can tell you your exact payment based on your actual loan terms, and they can walk you through the different repayment options available to you. Your servicer's contact information is on your loan documents or on StudentAid.gov if you have federal loans.
Frequently Asked Questions
Will my payment change if interest rates go up?
Federal student loans have fixed interest rates that never change. Private loans may have variable rates that adjust with market conditions, which would change your payment. Check your loan documents to see whether your rate is fixed or variable.
What happens if I pay more than my monthly payment?
Extra payments go directly toward your principal, which reduces the total interest you pay and shortens your repayment timeline. There are no penalties for paying extra on federal or most private loans. Ask your servicer to confirm there's no prepayment penalty before you start paying extra.
Can I change my repayment plan after I start repaying?
Yes. Federal loans allow you to switch between repayment plans at any time. If your income drops or your circumstances change, you can move to an income-driven plan. If your income rises, you might switch back to the standard plan to pay off the loan faster. Private loans typically do not allow plan changes.
Does my credit score affect my student loan payment?
Your credit score does not affect federal student loan payments — they're based on your loan balance, interest rate, and term. Private loan payments may be affected if you have a variable-rate loan, because some variable rates are tied to credit market conditions, not your personal credit score.
What if I have loans from multiple servicers?
Calculate the payment for each loan separately using its own balance, interest rate, and term. Add all the monthly payments together to see your total monthly obligation. If you have federal loans with different servicers, you may be able to consolidate them into a single Direct Consolidation Loan, which combines them into one payment.