Student Loan Calculator (Payment and Payoff with Extra Payments)
Enter the loan balance, interest rate and repayment term.
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Student Loan Calculator (Payment and Payoff with Extra Payments) by TheCalcTools
How the Student Loan Calculator (Payment and Payoff with Extra Payments) works
Student loans usually amortise with a fixed monthly payment. Paying extra each month goes straight to principal, cutting both the time and total interest.
With extra payment X, the payoff time is n = −ln(1 − B × i ÷ (P + X)) ÷ ln(1 + i). US federal loans also offer income-driven plans that this calculator does not model.
The formula
Worked example
Using the default values shown in the calculator:
| Loan balance | $35000 |
|---|---|
| Interest rate | 6.5 % |
| Repayment term (years) | 10 |
| Extra payment each month | $100 |
- 35,000 at 6.5% over 10 years: $397.42 a month and $12,690.15 of interest.
- Paying 100 extra clears it in 89 months and saves $3,504.15.
Result:
| Monthly payment | $397.42 |
|---|---|
| Total interest | $12,690.15 |
| Months to pay off with the extra payment | 89 |
| Interest saved by paying extra | $3,504.15 |
| Time saved | 2 years 7 months |
Frequently asked questions
Should I pay off student loans or invest?
Compare the loan rate with your expected after-tax investment return, and keep an emergency fund. Federal loans have protections that refinancing can remove.
Sources and further reading
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This calculator gives estimates for information only. It is not financial advice, and your lender's or provider's figures will govern. Rates, fees and rules vary. See our disclaimer.