Student Loan Refinance Calculator

The Student Loan Refinance Calculator compares your current student loan with a refinanced loan on the same balance, showing the monthly payment, total interest, and total cost of each, plus the monthly and lifetime savings if the new terms are better. Change the rate, the term, or both, and see immediately whether a lower payment also means a cheaper loan.

How it works

1. Validation: The balance and both terms must be greater than zero, and neither interest rate can be negative. Any problem returns an error naming the field to fix.
2. Processing: The standard amortization formula is applied twice: once with your current rate and remaining term, and once with the proposed rate and term, both on the same starting balance.
3. Breakdown: Each payment is multiplied across its term to get total payments; subtracting the balance leaves total interest. The calculator then differences the two scenarios into monthly savings, interest savings, and total savings.
4. Privacy: Your loan figures are processed in your browser and are never uploaded or stored.

Formula

For a loan with principal P, annual rate r expressed as a decimal, and n monthly payments, the monthly payment is:

$M=P\frac{\frac{r}{12}\left(1+\frac{r}{12}\right)^n}{\left(1+\frac{r}{12}\right)^n-1}$

At a zero rate, the payment is simply the balance divided by the number of months. Then:

$\text{Total interest}=\left(M\times n\right)-P$

$\text{Monthly savings}=M_{\text{current}}-M_{\text{new}}\qquad \text{Total savings}=\text{Total cost}_{\text{current}}-\text{Total cost}_{\text{new}}$

Input parameters

| Parameter | Unit | Realistic range | What it means | | --- | --- | --- | --- | | Current balance | USD | 1,000 to 200,000 covers most borrowers | What you still owe today, not what you originally borrowed | | Current interest rate | percent per year | 4 to 9 typical for federal loans; private loans vary wider | The rate on your existing loan | | Current remaining term | years | 1 to 30; 10 is the standard federal plan | How long you would keep paying at the current pace | | New interest rate | percent per year | the rate a lender has quoted or advertised for your credit profile | The refinance offer rate; fixed and variable offers behave differently | | New term | years | 5 to 20 offered by most refinance lenders | The repayment period of the new loan; longer terms cut the payment but usually raise total interest |

Worked example

You owe USD 50,000 at 6.8 percent with 10 years remaining, and a lender offers 4.5 percent over the same 10-year term:

1. Current payment: the amortization formula at a monthly rate of 6.8 / 100 / 12 over 120 payments gives USD 575.40 per month.
2. Current totals: 575.40 x 120 = USD 69,048 paid overall, of which 69,048 - 50,000 = USD 19,048 is interest.
3. New payment at 4.5 percent: USD 518.19 per month.
4. New totals: 518.19 x 120 = USD 62,183, of which USD 12,183 is interest.
5. Savings: USD 57.21 per month and about USD 6,865 of interest over the life of the loan.

Holding the term constant is what makes the comparison clean here: every dollar of the difference comes from the rate, not from stretching the loan.

Interpreting the result

Monthly savings and lifetime savings can point in opposite directions, and the lifetime figure is the one that measures whether refinancing actually helps. Extending a 10-year loan to 20 years at a lower rate will almost always show an attractive monthly saving while quietly adding thousands in total interest; if total savings comes out negative, the refinance makes you worse off despite the smaller payment.

Also weigh what does not appear in the arithmetic. A meaningful rate cut on a private loan is usually a straightforward win if the term does not grow. For a federal loan, the interest saving is only half the decision, because refinancing converts the loan to a private one and permanently ends the federal protections discussed in the limitations. A useful rule from this table: the larger the rate drop and the shorter the new term, the stronger the case; a small rate drop paired with a longer term rarely survives the total-savings test.

Choosing the right tool

• Loan Calculator: Use it to model a single loan from scratch, including an amortization view, when you are not comparing two scenarios.
• Debt Snowball Calculator: Use it when you have several debts and want a payoff order that clears the smallest balances first for momentum.
• Debt Avalanche Calculator: Use it instead when you want the mathematically cheapest payoff order, highest interest rate first, across multiple debts including student loans.

Limitations

This is a two-scenario estimate on fixed assumptions. It does not include lender origination fees, rate discounts for autopay, or the possibility that a quoted rate changes at approval, and it assumes both rates stay fixed for the full term, so a variable-rate offer can behave very differently. It also cannot value what you give up by refinancing federal loans: income-driven repayment plans, Public Service Loan Forgiveness and other forgiveness paths, generous deferment and forbearance, and death and disability discharge all end when a federal loan is refinanced into a private loan. Compare the interest saving against those protections, especially if your income is uncertain or you work in public service, before acting on a positive result.

Questions

Is a lower monthly payment always a good refinance?

No. A lower payment produced by a longer term usually means more total interest, even at a lower rate. Check the total savings figure: if it is negative, the new loan costs more over its life and the smaller payment is being bought with extra years of interest.

What do I lose by refinancing a federal student loan?

Refinancing pays off the federal loan with a private loan, and the federal benefits do not transfer. You lose access to income-driven repayment, loan forgiveness programs including Public Service Loan Forgiveness, federal deferment and forbearance options, and discharge on death or total disability. The change cannot be undone.

Does the calculator include lender fees?

No, there is no fee input, so compare the result against the actual offer documents. If a lender charges an origination fee, subtract it from the total savings figure yourself to get the true benefit, and check whether the quoted rate assumes an autopay discount you would actually use.

Sources and methodology

Payments use the standard fixed-rate amortization formula used across US consumer lending. The treatment of federal loan protections follows Consumer Financial Protection Bureau and Federal Student Aid (studentaid.gov) guidance, which cautions that refinancing federal loans into private loans permanently removes federal benefits. Rates in the worked example are illustrative; enter the exact figures from your servicer statement and a written lender quote for a decision-grade comparison.