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Student Loan Calculator

Student loan maths is the same as any other instalment loan, but the stakes are different: balances are large, terms are long, and the difference between a 10-year standard plan and a 25-year extended plan is often hundreds of dollars a month — and thousands in interest.

$

The federal standard plan runs 10 years; extended plans run 25.

$

Optional. Any amount above the scheduled payment goes to principal.

Results update as you type. Nothing leaves your device.

Monthly payment

$340.64

$30,000 over 120 months at 6.5%.

Monthly payment
$340.64
Total interest
$10,877.27
Interest as a share of what you pay
26.6%
Total paid
$40,877.27

Repayment term comparison

TermMonthly paymentTotal interestTotal paidChosen
10 years (standard)$340.64$10,877.27$40,877.27Yes
15 years$261.33$17,039.80$47,039.80
20 years$223.67$23,681.27$53,681.27
25 years (extended)$202.56$30,768.64$60,768.64

Each row is the same balance at the same rate: the only change is how long you take to repay it.

What paying extra every month would do

Extra per monthPaid off inTotal interestInterest savedTime saved
$25.009 years 1 month$9,782.37$1,094.9011 months
$50.008 years 4 months$8,892.17$1,985.101 year 8 months
$100.007 years 2 months$7,530.29$3,346.982 years 10 months
$200.005 years 7 months$5,777.86$5,099.414 years 5 months

Comparing against the 10-year plan above. Every extra dollar goes to principal, so it also removes the interest that dollar would have earned for the lender.

Stretching the same 30k balance from the 10-year standard plan to the 25-year extended plan lowers the payment by $138.08 a month but adds $19,891.37 of interest. Income-driven plans and forgiveness programmes are not modelled here, and they change that trade-off completely.

This calculator shows the payment on your balance and rate, compares the common repayment lengths side by side, and puts a price on paying a little extra each month.

How this student loan calculator works

How the payment is calculated

The scheduled payment comes from the standard amortization formula: M = P × i ÷ (1 − (1 + i)^−n), where P is the balance, i is the monthly rate and n is the number of payments. Interest is charged on the outstanding balance every month, so a 25-year plan spends far more of each payment on interest in the early years.

A $30,000 balance at 6.5% costs about $341 a month over 10 years, and about $203 a month over 25 years. The 25-year plan collects roughly $31,000 of interest against $11,000 on the 10-year plan.

Why the term matters more than the rate

A rate cut of half a percentage point is worth tens of dollars a month. Doubling the term is worth a hundred or more — which is why longer plans feel like relief. The interest column is the bill for that relief.

Extra payments attack the balance directly, and the saving compounds: $100 a month extra on a 10-year loan finishes it years early and removes interest that would otherwise have accrued on the whole remaining balance.

What is not modelled

This is a fixed-rate, fully amortizing loan. Federal income-driven repayment (IDR) plans recalculate the payment from your income each year and can forgive a remaining balance after 20 to 25 years; Public Service Loan Forgiveness forgives the balance after 120 qualifying payments. Those programmes are the main reason not to simply pick the shortest term.

Also excluded: subsidised deferment and forbearance (where the government pays interest), grace-period interest on unsubsidised loans, consolidation of several loans into a weighted-average rate, and any private-loan prepayment penalty.

Worked examples

Each example below was run through the calculator on this page when the site was built, so the numbers match what you see when you enter the same inputs.

$30,000 at 6.5% on the 10-year standard plan

Loan balance
$30,000.00
Interest rate
6.5%
Repayment term
10 years
Extra payment each month
$0.00

Monthly payment

$340.64

$30,000 over 120 months at 6.5%.

Monthly payment
$340.64
Total interest
$10,877.27
Interest as a share of what you pay
26.6%
Total paid
$40,877.27

The standard plan pays the loan off in 120 payments with roughly a third of the total cost going to interest.

The same balance on a 25-year extended plan

Loan balance
$30,000.00
Interest rate
6.5%
Repayment term
25 years
Extra payment each month
$0.00

Monthly payment

$202.56

$30,000 over 300 months at 6.5%.

Monthly payment
$202.56
Total interest
$30,768.64
Interest as a share of what you pay
50.6%
Total paid
$60,768.64

The payment falls by about 40%, but the interest bill nearly triples — the trade the comparison table makes visible.

10-year plan plus $100 a month

Loan balance
$30,000.00
Interest rate
6.5%
Repayment term
10 years
Extra payment each month
$100.00

Payoff time with extra payments

7 years 2 months

$340.64 scheduled plus $100.00 extra on $30,000 at 6.5%.

Monthly payment
$340.64
Total interest
$7,530.29
Interest as a share of what you pay
20.1%
Total paid
$37,555.14

Extra principal clears the loan years early and saves interest worth several times the extra money paid.

Graduate-school balance at 7.5%

Loan balance
$85,000.00
Interest rate
7.5%
Repayment term
10 years
Extra payment each month
$250.00

Payoff time with extra payments

7 years 4 months

$1,008.97 scheduled plus $250.00 extra on $85,000 at 7.5%.

Monthly payment
$1,008.97
Total interest
$25,758.17
Interest as a share of what you pay
23.3%
Total paid
$110,758.17

On a large balance the extra payment moves the payoff date by years, not months.

Frequently asked questions

How is the student loan monthly payment calculated?

With the standard amortization formula: monthly rate times balance, divided by one minus the monthly rate compounded over the number of payments. Interest is charged on the remaining balance each month, so the split between principal and interest shifts over the term.

Should I choose the 10-year or the 25-year plan?

The shorter term always costs less in total. The longer term is justified when the lower payment is necessary to keep the account current, or when you are pursuing federal forgiveness — in those cases the plan is chosen for the outcome, not the interest bill.

Does paying extra help on a federal student loan?

Yes. There is no prepayment penalty, and extra payments go to principal once the month’s interest is covered. On newer federal loans you can usually direct the payment to a specific loan, which is worth doing: hit the highest rate first.

What is the difference between consolidation and refinancing?

Federal consolidation combines loans into one Direct Consolidation Loan at a weighted-average rate and keeps federal protections. Refinancing with a private lender replaces federal loans with a new loan at a market rate, which can be lower but permanently gives up IDR, PSLF and federal deferment options.

Can I refinance only part of my student loans?

Yes, and it is often the smart move: refinancing only the private loans, or only the highest-rate graduate loans, keeps the federal protections on the rest of the balance.

Is student loan interest tax deductible?

US taxpayers can generally deduct up to $2,500 of student loan interest paid each year, subject to income phase-outs, whether the loan is federal or private. The calculator does not model the deduction.

What happens if I stop paying?

Federal loans have specific delinquency and default rules, with rehabilitation options; private loans follow ordinary collections. In both cases the balance keeps accruing interest, so contact the servicer before the first missed payment rather than after.

Assumptions and sources

  • Payment and interest maths use the standard amortization formula with monthly compounding at one twelfth of the annual rate.
  • The 10-year standard plan is the default federal repayment plan; 15, 20 and 25-year terms reflect the common consolidated and extended plan lengths.
  • Income-driven repayment, forgiveness programmes, subsidised deferment and grace-period interest are outside the model.

Last reviewed 2026-09-14. This page is an estimate tool, not financial, tax or legal advice.Read the full disclaimer.

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