What goes into your monthly payment
Your student loan payment is built from three pieces: the principal (the money you borrowed), the interest (what the lender charges you to borrow it), and the loan term (how many months you have to pay it back). The lender calculates a fixed monthly amount that, if paid on time for the full term, will pay off both the principal and interest by the end.
The exact payment depends on which repayment plan you chose. Federal loans offer multiple plans—Standard, Income-Driven, Graduated—and each one spreads your debt over a different timeline, which changes your monthly number. Private loans usually have fewer options and are set by your lender's contract.
You do not need to do this math yourself. Your loan servicer (the company that collects your payments) will tell you the exact amount due each month. But understanding how it works helps you spot errors, compare plans, or see what happens if you pay extra.
Key Takeaways
- Your monthly payment is calculated by dividing your total loan balance by the number of months in your repayment plan, then adding interest charged each month.
- Federal loans let you choose among Standard (10 years), Graduated (10 years, starting low), and Income-Driven plans (20 to 25 years), each producing a different monthly amount.
- Your loan servicer provides your exact payment amount; you can also use the Federal Student Aid loan calculator or your lender's online portal to see the breakdown.
- Paying more than the minimum goes entirely to principal and shortens your loan term, but does not change your required monthly payment.
- Interest accrues daily on unsubsidized loans, so the longer you wait to pay, the more you owe.
The Standard Repayment Plan formula
The Standard plan spreads federal loans over 10 years (120 months). The basic formula is: divide your loan balance by 120, then add the monthly interest charge. The interest portion shrinks each month because you owe less principal, so your payment stays the same but more of it goes to principal as time passes.
Example: You owe $30,000 at 5% annual interest. Divide $30,000 by 120 months = $250 principal per month. In month one, interest is $30,000 × 0.05 ÷ 12 = $125. Your payment is roughly $375. In month 12, you owe less principal, so interest drops to about $118, and your payment is about $368. The payment amount the servicer quotes you is the fixed number that keeps this math balanced across all 120 months.
You can calculate this yourself using the Federal Student Aid loan calculator at studentaid.gov, which asks for your loan amount, interest rate, and plan, then shows your monthly payment and total interest paid over the life of the loan.
Income-Driven plans and variable payments
Income-Driven plans (PAYE, REPAYE, IBR, ICR) calculate your payment as a percentage of your discretionary income—your gross income minus 150% of the federal poverty line for your household size. The payment changes each year when you recertify your income, so the monthly amount is not fixed like Standard or Graduated.
PAYE and REPAYE cap your payment at 10% of discretionary income. IBR caps it at 10% or 15% depending on when you took out the loan. If your income is very low, your payment may be $0, but interest still accrues on unsubsidized loans. After 20 to 25 years of payments (depending on the plan), any remaining balance is forgiven, though you may owe taxes on the forgiven amount.
To see what an Income-Driven payment would be, you need your most recent tax return or income estimate. The Federal Student Aid calculator lets you enter this information, or you can contact your servicer and ask them to estimate it based on your income.
How interest accrual changes your balance
Interest on federal loans accrues daily, meaning it is calculated and added to your balance every single day. On unsubsidized loans, you pay this interest whether you are in school, in deferment, or in forbearance. On subsidized loans, the government pays the interest while you are in school at least half-time.
If you do not pay accrued interest before your loan enters repayment, it capitalizes—meaning it gets added to your principal balance. Your next payment is then calculated on this larger number, so you end up paying interest on interest. This is why paying interest during school, if you can, saves money over the life of the loan.
The daily interest rate is your annual rate divided by 365. On a $30,000 loan at 5%, that is $30,000 × 0.05 ÷ 365 = $4.11 per day. Over a month, that is roughly $125, which matches the monthly calculation above.
Private loan payments and fixed terms
Private student loans are calculated the same way as federal loans—principal divided by months, plus monthly interest—but the terms are set by your lender's contract, not by federal law. Most private loans have a fixed interest rate and a fixed term (usually 5, 10, or 15 years), so your payment does not change.
Some private lenders offer variable-rate loans, where your interest rate adjusts based on market conditions, which means your payment can go up or down. Always check your promissory note to see whether your rate is fixed or variable and what your term is.
Your private lender's website or your monthly statement will show your exact payment. If you want to see the math, ask your lender for your interest rate and loan term, then use an online loan calculator (search "loan payment calculator") and enter those numbers.
What happens when you pay extra
Any payment above your required monthly amount goes directly to principal. This shortens your loan term and reduces the total interest you pay, but it does not lower your required monthly payment—you still owe the same amount each month, you are just finishing faster.
If you pay $500 instead of $375, the extra $125 goes to principal. Your next month's interest is calculated on a slightly smaller balance, so a tiny bit more of your regular payment goes to principal. Over years, this compounds and can cut years off your loan.
Some lenders charge a prepayment penalty if you pay off the loan early, though federal loans do not. Check your promissory note or ask your lender before making large extra payments.
Using online calculators and your servicer's tools
The Federal Student Aid loan calculator (studentaid.gov/loan-simulator) is free and does not require you to log in. Enter your loan amount, interest rate, and repayment plan, and it shows your monthly payment, total interest, and payoff date. It also lets you compare plans side by side.
Your loan servicer's website (Nelnet, Mohela, Great Lakes, or whoever collects your payments) has a portal where you can log in and see your exact balance, interest rate, and current payment. Many servicers also have a calculator tool built into their site.
If you are on an Income-Driven plan, your servicer can estimate your payment based on your income if you call or use their online portal. You will need your most recent tax return or a current income estimate.
Frequently Asked Questions
Can I calculate my payment if I have multiple loans?
Yes, but each loan is calculated separately. A $15,000 loan at 4% and a $15,000 loan at 6% do not average to 5%—each one has its own payment. Add up all the individual payments to get your total monthly bill. The Federal Student Aid calculator lets you enter multiple loans and shows the combined payment.
What if my interest rate is variable?
Variable rates change based on market conditions, so your payment may change too. Your lender will notify you when the rate adjusts. You can calculate your current payment using your current rate, but future payments depend on rate changes you cannot predict. Ask your lender what the rate cap is (the highest it can go) so you know the worst-case payment.
Does paying extra principal change my required payment?
No. Your required payment stays the same each month. Extra payments go to principal and shorten your loan term, but they do not reduce what you owe next month. You still have to pay the required amount; the extra just gets you out of debt faster.
How do I know if my servicer calculated my payment correctly?
Use the Federal Student Aid calculator or your lender's calculator with your loan amount, interest rate, and plan, and compare the result to what your servicer says you owe. If they do not match, contact your servicer and ask them to explain the difference. Errors do happen, and your servicer is required to correct them.
What happens to my payment if I go into deferment or forbearance?
Your required payment is suspended—you do not have to pay. But on unsubsidized loans, interest keeps accruing. When you exit deferment or forbearance, your payment resumes at the same amount, but your balance may be higher because of accrued interest that capitalized.