Student Loan Calculator

Student loan payments work like a financial seesaw — early payments are mostly interest, later payments are mostly principal. In the first years of a typical 10-year loan, roughly 60% of each payment goes to interest rather than reducing what you actually owe.

The math uses an amortization schedule where your payment stays the same, but the split between interest and principal changes each month. Interest is calculated on your remaining balance, so as the balance shrinks, more of your payment chips away at the actual debt.

This front-loaded interest structure explains why extra payments early in the loan term save dramatically more money than extra payments near the end. An extra $100 in year one might save $200 in total interest, while the same $100 in year nine saves only $20.

Use this calculator when deciding between repayment plans, evaluating whether to make extra payments, or comparing the true cost of different loan amounts before borrowing. It's most accurate for standard fixed-rate loans with level payments throughout the term.

Don't rely on this calculation for income-driven repayment plans, where payments change annually based on your income and family size. These plans require separate calculators that account for income changes, tax implications, and potential loan forgiveness after 20-25 years.

Also avoid using standard repayment calculations if you're likely to qualify for loan forgiveness programs. Public Service Loan Forgiveness and teacher forgiveness programs typically require income-driven payments, not the higher standard payments this calculator shows.

The biggest mistake is focusing only on monthly payment amount instead of total loan cost. Extending repayment from 10 to 20 years might cut your payment in half, but often doubles your total interest. A $30,000 loan at 6% costs $6,330 in interest over 10 years but $14,000 over 20 years.

Another common error is paying extra toward multiple loans randomly instead of targeting the highest interest rate first. If you have loans at 4% and 7%, every extra dollar should go to the 7% loan until it's gone. This avalanche method saves more money than spreading payments evenly across all loans.

Many borrowers also refinance federal loans to get lower rates without understanding they're giving up federal protections like income-driven repayment and forgiveness programs. Once you refinance federal loans with a private lender, you can't get those benefits back, even if your financial situation changes.

Student loan payments follow the standard amortization formula: P = L[c(1 + c)^n]/[(1 + c)^n - 1], where P is your monthly payment, L is the loan amount, c is your monthly interest rate (annual rate divided by 12), and n is the total number of payments.

The key insight is that your monthly interest charge equals your remaining balance multiplied by the monthly interest rate. On a $30,000 loan at 6% annual interest, your first month's interest charge is $150 ($30,000 × 0.005). The rest of your payment reduces the principal balance.

Extra payments attack the principal directly, reducing future interest charges. Each extra dollar saves you approximately your interest rate in total interest over the loan's life. On a 6% loan, each extra dollar saves about $0.60 in interest, though the exact savings depend on when you make the payment.

Loan servicers often apply extra payments to future months rather than principal reduction, which doesn't save you any interest. Always specify that extra payments should go toward principal only and check your next statement to verify they applied it correctly.