See when your student loans will be paid off, how much interest you will pay, and how much time and money an extra monthly payment saves.
By TanLabs Editorial Team · Reviewed: page results cross-checked against the free spreadsheet · Last updated · Runs in your browser – nothing you type is sent anywhere
With loan balance $30,000, interest rate 6.5%, current monthly payment $340, extra payment each month $100:
Paid off in 7 yr 2 mo (86 payments) with $100.00 extra
Interest $7,545.21 · saves $3,363.82 and 35 months vs. 10 yr 1 mo without extra
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Monthly rate r = APR ÷ 12. Each month: interest = balance × r; the payment (regular + extra) first covers interest and the rest reduces the balance, until the balance reaches zero. Interest saved = total interest without the extra − total interest with it.
Formula source: Monthly amortization (APR ÷ 12), extra payments applied to principal – the actuarial method of Regulation Z. CFPB Regulation Z, Appendix J – actuarial (amortization) method · CFPB – what is amortization? · Federal Student Aid – interest rates and fees
Written and checked by the TanLabs Editorial Team · Last updated
$30,000 at 6.5%, regular payment $340 a month:
| $30,000 at 6.5%, $340/month + extra | Payoff time | Total interest | Interest saved |
|---|---|---|---|
| $0 | 10 yr 1 mo | $10,909.03 | $0.00 |
| $50 | 8 yr 4 mo | $8,912.94 | $1,996.09 |
| $100 | 7 yr 2 mo | $7,545.21 | $3,363.82 |
| $200 | 5 yr 7 mo | $5,786.56 | $5,122.46 |
| $500 | 3 yr 4 mo | $3,430.93 | $7,478.10 |
An extra $100 a month cuts almost three years and about $3,364 of interest. Extra payments early in the loan save the most because the balance is highest.
There is no prepayment penalty on federal or private student loans. Paying early makes most sense on the highest-rate loans; keep an emergency fund and any employer 401(k) match first.
Ask your servicer to apply extra money to principal on your highest-interest loan (the "avalanche" order). Otherwise it may be applied to the next month's bill instead.
Extra payments can still cut interest, but if you expect forgiveness under an income-driven plan or Public Service Loan Forgiveness, paying extra may not help. Check studentaid.gov first.
Refinancing with a private lender can lower the rate but removes federal benefits such as income-driven repayment and forgiveness programs.
Up to $2,500 of student loan interest a year may be deductible, with income limits. Check IRS Topic 456.
Most federal loans use simple daily interest on the principal balance; monthly amortization like this calculator gives very close results.
Sources: Federal Student Aid – repayment plans · Federal Student Aid – interest rates and fees