Student Loan Repayment Calculator

What this calculator does

This student loan repayment calculator compares what you would pay under a standard amortizing schedule against an income-driven payment based on your earnings. Enter your balance, interest rate, annual income, repayment period, and any extra payment, and it returns the standard monthly payment, the income-based monthly figure, the total interest, and what overpaying saves.

Those two payment figures answer different questions. The standard payment tells you what it costs to be finished in ten years. The income-driven payment tells you what fits in your budget right now. Most borrowers need both numbers before they can sensibly choose a plan.

When to use it

The obvious moment is the end of your six-month grace period, when you are placed on standard repayment by default and have to decide whether to stay there. Comparing the standard payment against your actual take-home pay is a five-minute exercise that determines the next decade of your finances.

It is equally useful when income changes — a raise, a new job, a move into or out of public service. And it matters most when you are weighing forgiveness. If you are pursuing PSLF, the goal is to minimize payments over 120 months rather than minimize total interest, which inverts the usual advice. Seeing both totals side by side is what makes that trade-off concrete.

Understanding the inputs

Loan balance should combine all federal loans you intend to repay together, though note that different loans can carry different rates. Interest rate is the weighted average if you are grouping several; federal rates are fixed for the life of the loan and set annually by Congress.

Annual income drives the income-driven figure. Use adjusted gross income, since that is what servicers work from, and remember that filing separately from a spouse can reduce the payment on some plans. Repayment period is ten years on the standard plan and 20 or 25 on income-driven plans. The extra payment field is only meaningful if you are not pursuing forgiveness.

How is this calculated?

Standard: Monthly Payment = P[r(1+r)^n]/[(1+r)^n-1]. Income-driven: 10% of discretionary income.

A worked example

Take a $38,000 balance at 6.5 percent with a $52,000 salary. Standard repayment over ten years is about $431 a month, with total interest of roughly $13,778. An income-driven plan at 10 percent of discretionary income, using a poverty guideline threshold near $23,475 for a single borrower, gives about $238 a month — nearly $200 less.

But that lower payment stretches the term and adds interest. Going the other way, adding $150 to the standard payment clears the loan in about 81 months instead of 120 and cuts total interest to roughly $9,031, saving around $4,747 and finishing more than three years early.

Limitations and assumptions

The income-driven figure here is a simplified 10 percent of discretionary income. Actual federal plans differ in their percentage, their poverty multiple, their treatment of spousal income, and their interest subsidies, and the available plans have changed repeatedly through legislation and litigation. Treat the figure as indicative and check the Federal Student Aid loan simulator for your specific situation.

The calculator does not model capitalized interest, deferment, forbearance, subsidized loan interest benefits, forgiveness at the end of an IDR term, or the potential tax on forgiven amounts. It also assumes a single blended rate. For PSLF planning in particular, your servicer's payment count is the number that governs.