How to use this calculator
- Enter your total student loan balance, the interest rate and your current monthly payment. Your loan servicer’s website shows all three.
- Enter an extra amount you could pay each month, a one-time extra payment, or both.
- Read the result: your payoff date as you pay today, how much sooner extra payments would clear the loans, and the interest you’d save.
If you have several loans at different rates, use the balance-weighted average rate, or run each loan separately. Nothing you enter is sent anywhere: the math runs in your browser.
The formula behind the numbers
Interest this month = Balance × Interest rate ÷ 12
New balance = Balance + Interest − Payment − Extra payment
Standard 10-year payment = Balance × r ÷ (1 − (1 + r)−120), where r = rate ÷ 12
The calculator repeats this month by month until the balance reaches zero, once at your current payment and once with your extra payments. The one-time payment is applied in the first month. Extra money is assumed to go to principal.
Worked example
These are the numbers the calculator loads with: $32,000 at 6.5%, with a $365 monthly payment, close to the standard 10-year payment of $363.35.
| As you pay today | With $100 extra a month | With a $3,000 one-time payment | |
|---|---|---|---|
| Paid off in | 120 months (10 years) | 87 months (7 years 3 months) | 105 months (8 years 9 months) |
| Total interest | $11,523 | $8,150 | $9,053 |
| Interest saved | – | $3,373 | $2,470 |
An extra $100 a month takes nearly three years off and saves $3,373. A single $3,000 payment made now saves $2,470, because that money never collects interest again.
Making extra payments count
- Tell your servicer to apply extra money to principal. Otherwise it may be used to push back your next due date instead of reducing the balance.
- Target your highest-rate loan first. If you have several loans, extra money on the highest rate saves the most. The debt avalanche calculator can plan the order.
- Check before paying extra on federal loans if you’re working toward forgiveness, such as Public Service Loan Forgiveness. Paying early can reduce the amount that would be forgiven.
- Keep an emergency fund. Money paid toward a loan is hard to get back if you need it.
Frequently asked questions
How long does it take to pay off student loans?
On the federal standard repayment plan, 10 years. Other plans, such as extended and income-driven plans, can take 20 years or longer. Enter your balance, rate and payment above to see your own date.
Is it better to pay extra monthly or make a lump sum payment?
Both help. A lump sum paid early saves more per dollar because it stops interest right away. Regular extra payments add up to more money over time. Try both above to see which fits your budget.
Why might my servicer’s numbers be different?
Federal student loans usually charge simple interest that accrues daily, and servicers apply payments on the date they arrive. This calculator uses monthly interest, which is very close. Rate changes, deferment, forbearance and capitalized interest aren’t included.
Should I pay off student loans early or invest?
It depends on your loan rate, your other goals and your tolerance for risk. Paying off a loan gives a guaranteed return equal to its interest rate. Many people build an emergency fund and capture any employer retirement match first.
Is my information saved or shared?
No. The calculator runs entirely in your browser. If you use “Copy link to results”, your numbers are stored only in that link, so share it only with people you trust.
This calculator is for education and planning. It assumes a fixed rate and on-time payments, and it isn’t financial advice. For federal loans, check repayment and forgiveness options at StudentAid.gov before changing your plan.