Student Loan Calculator
Repayment plan and total interest.
Reviewed by the Calculation Machine team · Updated 24 October 2026 · How we check our maths
Your values
ⓘ Live results
- Monthly payment
- $423.79
- Payoff time
- 10 yr 0 mo
- Total interest
- $12,854.64
- Total repaid
- $50,854.64
- Interest saved by extra payments
- $0.00
Quick answer
A fixed student loan payment is P × r ÷ (1 − (1 + r)⁻ⁿ), where P is the balance, r the monthly rate and n the number of months. A $38,000 balance at 6.1% on the 10-year standard plan costs $423.79 a month, with $12,854.64 of interest over the life of the loan. Adding $150 a month clears it in 6 years 9 months.
What the Student Loan calculator does
This calculator works out the level monthly payment for a student loan balance at a fixed rate and term, the total interest you will pay, and how much sooner you finish — and how much interest you save — by paying extra each month.
It matches the Standard Repayment Plan for federal Direct Loans (fixed payments over up to 10 years) and the extended plan (up to 25 years for larger balances), as well as fixed-rate private loans. If you have several loans, enter the total balance and a weighted average rate: multiply each balance by its rate, add the results, and divide by the total balance.
It does not model income-driven repayment plans, where payments depend on income and family size, nor forgiveness programs such as Public Service Loan Forgiveness. For those, use the Loan Simulator on the Federal Student Aid website. Federal plan options are also changing for loans made after mid-2026 under 2025 legislation, so confirm which plans apply to your loans there. To compare paying off loans against other debts, the debt avalanche calculator ranks balances by interest rate.
The formula
Monthly payment M = P × r ÷ (1 − (1 + r)⁻ⁿ) With extra E: balance = balance × (1 + r) − (M + E) each month until it reaches 0 Interest saved = M × n − total paid with extra
| Symbol | Meaning | Unit |
|---|---|---|
| P | Current loan balance (principal plus any capitalized interest) | $ |
| r | Monthly interest rate = annual rate ÷ 12 ÷ 100 | decimal |
| n | Repayment term in months (years × 12) | months |
| E | Extra amount paid every month | $ |
This is the standard fixed-payment amortization used by federal loan servicers for the Standard and Extended plans. Federal Direct Loans actually accrue simple interest daily, so real totals differ by a few dollars. Graduated plans, income-driven plans, and any interest that capitalizes after deferment or forbearance are not modeled.
Worked examples
Standard 10-year repayment
A graduate with $38,000 of loans at a 6.1% weighted average rate on the 10-year standard plan.
Inputs
- Loan balance38000 $
- Interest rate6.1 %
- Repayment term10 years
- Extra monthly payment0 $
Result
- Monthly payment$423.79
- Payoff time10 yr 0 mo
- Total interest$12,854.64
- Total repaid$50,854.64
- Interest saved by extra payments$0.00
The payment is $423.79 a month, and about $12,855 of the $50,855 total is interest. This is the baseline to compare every other option against.
Paying $150 a month extra
The same $38,000 at 6.1%, but the borrower adds $150 a month toward principal.
Inputs
- Loan balance38000 $
- Interest rate6.1 %
- Repayment term10 years
- Extra monthly payment150 $
Result
- Monthly payment$573.79
- Payoff time6 yr 9 mo
- Total interest$8,448.36
- Total repaid$46,448.36
- Interest saved by extra payments$4,406.28
The loan is gone in 6 years 9 months instead of 10 years, saving $4,406.28 in interest. Ask the servicer to apply extra payments to principal on the highest-rate loan first.
Extended 25-year plan
The same $38,000 balance stretched over 25 years, which federal borrowers with more than $30,000 of Direct Loans can choose.
Inputs
- Loan balance38000 $
- Interest rate6.1 %
- Repayment term25 years
- Extra monthly payment0 $
Result
- Monthly payment$247.16
- Payoff time25 yr 0 mo
- Total interest$36,148.79
- Total repaid$74,148.79
- Interest saved by extra payments$0.00
The payment drops to $247.16, but total interest rises to $36,148.79 — nearly three times the 10-year cost. Use a longer term for breathing room, then pay extra when you can.
How term length changes payment and total interest
All rows use a $38,000 balance at 6.1%. Longer terms lower the monthly payment but sharply increase the interest you pay, because the balance stays high for longer.
| Term | Monthly payment | Total interest | Total repaid |
|---|---|---|---|
| 10 years | $423.79 | $12,854.64 | $50,854.64 |
| 15 years | $322.72 | $20,090.00 | $58,090.00 |
| 20 years | $274.44 | $27,865.74 | $65,865.74 |
| 25 years | $247.16 | $36,148.79 | $74,148.79 |
Should you refinance student loans?
Refinancing with a private lender replaces your loans with one new loan, ideally at a lower rate. Rerun this calculator with the new rate and term to see the saving: for example, the same $38,000 over 10 years at 4.5% would cost $393.83 a month and $9,259.11 in interest, about $3,600 less than at 6.1%.
Before refinancing federal loans, weigh what you give up: income-driven repayment, deferment and forbearance options, and eligibility for forgiveness programs such as Public Service Loan Forgiveness. These protections cannot be restored once loans become private. Refinancing private loans carries less of that trade-off.
Where extra payments do the most good
- Target the highest rate first. If you have several loans, extra money on the highest-rate loan saves the most interest — the avalanche method.
- Pay interest during grace periods. Unpaid interest on unsubsidized loans can be added to the principal at certain points, after which you pay interest on interest.
- Use autopay. Federal servicers offer a 0.25 percentage point rate reduction for automatic debit, and many private lenders offer a similar discount.
- Keep an emergency fund first. Federal loans offer payment relief options in hardship, so building savings before prepaying is reasonable. Higher-rate credit card debt should normally be cleared before extra student loan payments.
How to use the Student Loan Calculator
- 1Enter your total student loan balance from your servicer's website or studentaid.gov.
- 2Enter the interest rate, or a weighted average rate if you have several loans.
- 3Enter the repayment term in years: 10 for the federal standard plan, up to 25 for extended, or your private loan's term.
- 4Optionally add an extra monthly payment to see the faster payoff and interest saved.
Frequently asked questions
How long does it take to pay off student loans?
The federal standard plan takes 10 years, extended plans up to 25 years, and income-driven plans 20–25 years. With extra payments, many borrowers finish sooner — $150 extra a month cuts a 10-year, $38,000 loan at 6.1% to under 7 years.
How is student loan interest calculated?
Federal student loans use simple daily interest: balance × annual rate ÷ 365 for each day. A $38,000 balance at 6.1% accrues about $6.35 a day.
Is it better to pay extra on student loans or invest?
Paying extra earns a guaranteed return equal to your loan rate. Most people first capture any employer retirement match, then compare the loan rate with expected after-tax investment returns.
Can I deduct student loan interest?
In the US you can deduct up to $2,500 of student loan interest a year if your income is under the IRS phase-out limits, which change annually. Your servicer sends Form 1098-E showing interest paid.
What is a weighted average interest rate?
It is the average of your loan rates weighted by balance. For $20,000 at 5% and $10,000 at 7%: (20,000 × 5 + 10,000 × 7) ÷ 30,000 = 5.67%.
References
- Repayment plans for federal student loans — Federal Student Aid, US Department of Education
- Publication 970, Tax Benefits for Education — Internal Revenue Service
About this calculator
- Built and reviewed by the Calculation Machine team · How we build and test calculators
- Last reviewed: October 24, 2026
- Report an error