Reviewed by LoanCalcly Editorial · Published September 20, 2026
The standard schedule, on a $30,000 loan
A $30,000 balance at 6.53% over the standard 10-year term costs $341.10 a month and $10,932 in interest — more than a third of the original balance again. Because the term is short and the balance is large, the early years are interest-heavy in the same way a mortgage is, just compressed.
Here is what happens when you add to the payment. The extra money does not reduce next month's bill; it removes months from the end of the loan:
| Extra per month | Payment becomes | Paid off in | Total interest | Interest saved |
|---|---|---|---|---|
| $0 | $341.10 | 120 months | $10,932 | — |
| $50 | $391.10 | 100 months | $8,936 | $1,996 |
| $100 | $441.10 | 86 months | $7,567 | $3,365 |
$30,000 at 6.53% over 10 years. Assumes a simple-interest instalment loan with no prepayment penalty. Figures rounded to the nearest dollar.
What changes when the balance is bigger
Student loan balances are frequently larger than $30,000. Scaling the same term and rate to a $50,000 balance gives a payment of $568.50 and $18,220 of interest — the interest bill scales almost exactly with the balance, because at the same rate and term the whole schedule scales. That linearity is useful: the numbers above can be multiplied to estimate a loan of any size at 6.53% over ten years.
What does not scale linearly is the effect of an extra payment, because a fixed extra amount does proportionally less work on a bigger balance. On a $50,000 loan, $100 a month extra buys noticeably less time saved than it does on a $30,000 one.
Federal and private loans are not the same product
Federal loans
- Rates are set by statute each year and fixed for the life of the loan. They do not depend on your credit score.
- Income-driven repayment plans set the payment from your income rather than the balance, and generally forgive what remains after a set number of years. The available plans and their terms change, so verify against the official servicer rather than any summary.
- Forgiveness programmes exist for defined public service careers, generally after a set number of qualifying payments.
- Deferment and forbearance can pause payments in defined circumstances — but see the capitalisation warning below.
Private loans
- Rates depend on credit — yours or a co-signer's. This is where a co-signer makes the largest difference.
- No income-driven plans and no forgiveness in the federal sense. The contract terms are what you get.
- Terms are often shorter, which raises the payment and lowers the total interest.
The two traps worth knowing before you choose a strategy
Capitalisation
If you are not paying interest while in school, during a grace period, or while payments are paused, that interest does not disappear. It is added to the principal at defined points — commonly when the grace period ends — and from then on it accrues interest itself. The effect is that a balance can be larger after graduation than the amount originally borrowed, and the standard repayment schedule starts from the larger figure. If you can pay interest during school, even partially, it is one of the highest-return things you can do.
The forgiveness versus prepayment conflict
If you are on an income-driven plan and expect a remaining balance to be forgiven, extra payments reduce the amount that would have been forgiven — which means the return on them can be zero or negative. The arithmetic that makes $100 a month look excellent on a standard schedule reverses entirely on a forgiveness track. Decide which track you are on before deciding whether to prepay.
Refinancing deserves the same care. A lower rate from a private lender can be a genuine saving on a standard schedule, but it permanently retires the federal protections listed above. Run the refinance break-even arithmetic first, then ask what the protections you are giving up are worth.
Frequently asked questions
What interest rate should I enter?
Whatever is on your loan documents. Federal student loan rates are set each year by statute and then fixed for the life of that loan, so the rate you were given when you borrowed is the rate you keep. Private loans are credit-based and vary by lender. The 6.53% used in the examples here is illustrative, not a current quote.
Why does paying a little extra help so much?
Because student loans amortise over a relatively short term with a relatively large balance, so a large share of every early payment is interest. Anything above the scheduled payment goes entirely to principal, and every dollar of principal removed saves interest for every remaining month of the loan.
Should I pay extra on my student loans or invest the money?
There is no universal answer, and anyone who gives you one is guessing about your circumstances. Paying extra earns a guaranteed return equal to your interest rate. Investing has a higher expected return over long periods but no guarantee and no liquidity. Two things worth weighing: an emergency fund matters more than either, and if your loan is on an income-driven plan heading for forgiveness, extra payments can reduce the amount forgiven.
What happens if I consolidate or refinance?
Consolidating federal loans through the government combines them into one loan at a weighted average rate, which is mostly an administrative simplification. Refinancing with a private lender can lower the rate, but it converts federal loans into private ones — and with them you give up income-driven repayment, forgiveness programmes, and federal deferment and forbearance options. That trade deserves careful thought before it is made.
What is interest capitalisation?
It is when unpaid interest is added to the principal balance, so that future interest is charged on the larger amount. It commonly happens at the end of the grace period and after deferment or forbearance. It is the reason a loan balance can be higher after graduation than the amount originally borrowed.
Does this calculator cover income-driven repayment?
No. Income-driven plans set the payment as a percentage of discretionary income rather than from the balance, so they cannot be modelled from loan amount, rate and term alone. This calculator covers the standard fixed instalment schedule, which is what most private loans use and what federal loans default to.
Other calculators
- Mortgage calculator — Monthly payment with property tax, home insurance, HOA and PMI folded in — the number that actually leaves your account, not just principal and interest.
- Auto loan calculator — Work out the amount financed from price, down payment, trade-in and sales tax, then see what the monthly payment really costs over 48, 60 or 72 months.
- Personal loan calculator — Unsecured borrowing at the rates lenders actually quote, with the origination fee maths that decides whether the money is worth taking.
- Amortization schedule — The full month-by-month and year-by-year breakdown of a fixed-rate loan, and how much interest an extra payment removes from the end of it.
Guides that go with it
- How loan amortization works — The formula term by term, a worked month-by-month example, when principal finally overtakes interest, and why extra early payments save so much.
- How to compare loan offers — Why the headline rate is not the comparison, the three numbers that are, and how to work out whether discount points are worth paying.
- APR vs interest rate — What each number actually measures, what APR leaves out, and the cases where comparing APR will lead you to the wrong lender.
This calculator is educational and is not financial advice, and its output is an estimate — lenders apply their own fees, rounding rules and day-count conventions. Every figure was produced by the same calculator code and independently recomputed before publication. Spot an error? Tell us — see also our disclaimer.