Extra Student Loan Payment Calculator

Paying even a little extra on student loans each month can save thousands in interest and take years off repayment. This calculator shows exactly how much an extra payment saves, so you can decide whether it's worth it compared with other goals.

What this calculator does

Enter your loan balance, interest rate, current monthly payment and the extra amount you could pay each month. It shows:

• the interest you'd save,
• the time you'd save,
• your payoff time with and without the extra payment, and
• your total interest with the extra payment.

The chart compares your balance over time on both paths.

The formula in plain English

Each month, interest is charged on the remaining balance: balance × interest rate ÷ 12. Your payment first covers that interest; the rest reduces the balance.

An extra payment goes entirely to principal. A lower balance means less interest next month, so more of each later payment reduces principal too. That snowball effect is why small extra payments save more than you might expect.

The calculator runs both versions month by month until the balance reaches zero and compares total interest and months.

Interest saved = interest without extra − interest with extra.

Time saved = months without extra − months with extra.

A worked example

Dr. Ahmed has $180,000 in student loans at 6.8% and pays the 10-year standard payment of about $2,071 a month. He could add $500 a month.

• Without the extra: about 10 years, with roughly $68,600 in interest.
• With the extra: about 7.5 years (90 months).
• Interest saved: about $18,600.
• Time saved: about 31 months.

That $500 a month is $45,000 of extra payments over 7.5 years, and it saves about $18,600 in interest, a guaranteed 6.8% return on that money.

Why it matters at each career stage

If you're: Resident / fellow

Extra payments during training are hard and often not the best use of money. If you're on an income-driven plan and might pursue PSLF, make your required payment and build an emergency fund first.

If you're: Employed

The first few years after training are when extra payments make the biggest difference. Many new attendings choose a fixed extra amount, such as the difference between their resident and attending take-home, and set it on autopay.

If you're: Practice owner

Practice owners have competing uses for cash: practice loans, equipment and retirement plans. Compare interest rates: pay down the highest-rate debt first, and make sure your retirement contributions are capturing any tax savings.

When extra payments don't make sense

You're pursuing forgiveness. With PSLF or long-term income-driven forgiveness, extra payments shrink a balance that would have been forgiven.

You don't have an emergency fund. Money paid to a loan is hard to get back. Build three to six months of expenses first.

You're missing a retirement match. An employer match is an instant return that's hard to beat.

You have higher-rate debt. Credit cards and personal loans should usually be paid first.

Lump sums work too

You don't have to pay extra every month. A bonus, tax refund or moonlighting check applied to principal has the same effect as spreading it out, and the earlier in the loan it goes in, the more interest it saves. Many people combine a modest monthly extra with one or two lump sums a year.

If you have several loans, send the extra to one loan at a time instead of splitting it. Paying off a single loan completely frees up its required payment, which you can then add to the next loan.

Getting started

Set the extra payment as a separate automatic payment on payday so it happens without thinking. Raise it each time you get a raise. When the loan is gone, redirect the whole payment to investing.

Next, compare refinancing, see whether to invest instead, or plan a full payoff with the student loan payoff calculator.