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Mortgage & Loans
Student Loan Calculator — Monthly Payment, Total Interest & Payoff
What that loan balance really costs per month — and how an extra payment changes everything
A student loan calculator turns a scary-looking balance into the only two numbers that fit in a budget: what you pay each month and what the loan costs you in total. Most graduates know their balance and their interest rate but have never seen how those translate into a monthly check or a 10-year interest bill — and that gap is where overpaying quietly happens.
Federal student loans use standard amortization, the same math behind a car loan or mortgage. Each fixed monthly payment covers that month's interest first, and whatever is left chips away at the principal. The formula is:
M = P × r × (1 + r)ⁿ ÷ ((1 + r)ⁿ − 1)
where P is your loan balance, r is the monthly interest rate (the annual rate ÷ 12 ÷ 100), and n is the number of payments (years × 12).
Worked example. Say you owe $30,000 at 6% on the standard 10-year plan. Then r = 6 ÷ 1,200 = 0.005 and n = 120. Plugging in, M ≈ $333.06 per month. Over 120 payments that's $39,967 paid in, so you hand the lender about $9,967 in interest on top of the $30,000 you borrowed.
Now the part that saves real money: paying extra. Add just $50/month to that payment and the loan is gone in about 8 years 4 months instead of 10, with roughly $1,800 less interest — because every extra dollar lands directly on principal, shrinking the balance that interest is charged on. This calculator shows that side-by-side: your standard payoff versus your accelerated payoff, plus the interest you'd save.
A quick word on loan types. Federal loans (Direct Subsidized, Unsubsidized, PLUS) have fixed rates set by Congress, flexible plans (Standard, Graduated, income-driven), and protections like deferment and forgiveness. Private loans from banks or credit unions often carry variable rates, stricter terms, and few of those safety nets. This tool models a fixed-rate standard plan, which is the right baseline for federal loans and fixed private loans alike.
The most common mistake is dividing the balance by the number of months and calling that your payment — that ignores interest entirely and badly underestimates the real cost. Amortization charges interest on the remaining balance every single month, which is exactly what this calculator does for you.
This tool provides informational estimates only, not financial advice or a loan offer; your actual rate, payment, and terms are set by your loan servicer.
Calculator
Fill in the fields and click "Calculate" for instant results.
📰 Formula
• Monthly rate r = annual rate ÷ 12 ÷ 100 • Number of payments n = years × 12 • Monthly payment M = P × r × (1 + r)ⁿ ÷ ((1 + r)ⁿ − 1) • Total paid = M × n • Total interest = (M × n) − P • With extra: each month, balance = balance + interest − (M + extra), until balance ≤ 0
📰 Formula
• Monthly rate r = annual rate ÷ 12 ÷ 100 • Number of payments n = years × 12 • Monthly payment M = P × r × (1 + r)ⁿ ÷ ((1 + r)ⁿ − 1) • Total paid = M × n • Total interest = (M × n) − P • With extra: each month, balance = balance + interest − (M + extra), until balance ≤ 0
🧪 Worked examples
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Example 2
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Example 3
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Example 4
⚠️ Common mistakes
- Dividing the balance by the number of months and ignoring interest entirely.
- Using the annual rate directly instead of dividing it by 12 (and by 100) for the monthly rate.
- Mixing up the term in years with the number of payments (multiply years by 12).
- Assuming a longer term is cheaper — it lowers the monthly payment but raises total interest.
💡 Tips
- Every extra dollar goes straight to principal, so even small additions shorten the loan and cut interest fast.
- Tell your servicer to apply extra payments to principal, not to push your due date forward.
- The standard 10-year plan costs the least interest; income-driven and extended plans lower the payment but cost more over time.
Embed this calculator on your site
Copy the code below and paste it into the HTML of your site or blog.
<iframe src="https://www.calcnimbus.com/embed/student-loan-calculator" width="100%" height="500" frameborder="0" style="border:1px solid #eee;border-radius:12px"></iframe>
❓ Frequently asked questions
How is a student loan monthly payment calculated?
It uses standard amortization: M = P × r × (1+r)ⁿ ÷ ((1+r)ⁿ − 1), where P is your balance, r is the annual rate ÷ 1200, and n is the term in years × 12. A $30,000 loan at 6% over 10 years comes to about $333 per month.
What is the monthly payment on a $30,000 student loan?
At 6% on the standard 10-year plan, a $30,000 student loan is about $333 per month, with roughly $9,967 in total interest. A higher rate or longer term changes both numbers.
How much will I pay in total interest?
Multiply the monthly payment by the number of payments, then subtract the balance. A $30,000 loan at 6% over 10 years totals about $39,967 paid, which is roughly $9,967 of interest on top of the principal.
Does paying extra each month really help?
Yes, a lot. Extra payments go straight to principal, shrinking the balance that interest is charged on. Adding $50/month to a $30,000 loan at 6% pays it off about 20 months early and saves around $1,800 in interest.
What's the difference between federal and private student loans?
Federal loans have fixed rates set by Congress, flexible repayment plans, and protections like deferment, income-driven plans, and forgiveness. Private loans from banks or credit unions often have variable rates, fewer protections, and stricter terms.
What is the standard repayment term for student loans?
The federal standard plan is 10 years (120 fixed monthly payments). Extended and income-driven plans can run 20–25 years, which lowers the monthly payment but increases the total interest you pay.
Is a longer repayment term cheaper?
No. A longer term lowers your monthly payment but stretches interest over more years, so you pay more in total. A shorter term costs more per month but far less interest overall.
Does this calculator account for variable rates or fees?
No. It assumes a single fixed interest rate for the full term, which fits federal loans and fixed private loans. Variable-rate private loans can change over time, so treat the result as an estimate for those.
Should I refinance my student loans?
Refinancing into a lower rate can cut your payment and total interest, but refinancing federal loans into a private loan gives up federal protections like income-driven plans and forgiveness. Compare the rate savings against what you'd lose before deciding.