Calculate your monthly payment, total interest, and payoff date for federal or private student loans. See how extra payments accelerate payoff.
Loan Details
2025–26 federal undergrad rate: 6.53%
See how extra payments save interest and time
Repayment Summary
The Student Loan Calculator estimates your standard monthly payment, total interest, and full repayment cost for federal or private student loans, based on your balance, interest rate, and repayment term.
It also models the impact of extra monthly payments — a common strategy for private loans or federal loans with rates above ~6-7% — showing how much faster you'd pay off the balance and how much interest you'd save by paying even a modest amount more each month.
M = P × [r(1+r)ⁿ] / [(1+r)ⁿ − 1]The same amortization formula used for any installment loan. For federal loans, P, r, and n are typically fixed by your loan terms and the standard 10-year repayment plan; income-driven plans instead cap payments as a percentage of discretionary income rather than using this formula directly.
Example 1: $35,000 federal undergrad balance at 6.53% over 10 years
P = $35,000, the 2025-26 Direct Loan undergrad rate of 6.53%, n = 120 payments (standard plan).
Monthly payment ≈ $397.58 — total interest ≈ $12,709.60, total repaid ≈ $47,709.60.
Example 2: Same loan, with an extra $100/month
Same $35,000 balance and 6.53% rate, but paying $497.58/month instead of the standard $397.58.
Payoff time drops to roughly 7 years 7 months (about 29 months earlier) and total interest falls to around $9,500 — saving roughly $3,200.
Example 3: $80,000 grad PLUS loan at 9.08% over 15 years
P = $80,000, the 2025-26 Direct PLUS rate of 9.08%, n = 180 payments.
Monthly payment ≈ $814.46 — total interest ≈ $66,602.80, total repaid ≈ $146,602.80, illustrating why graduate borrowers often explore income-driven plans.
Methodology
Standard monthly payment: M = P×r(1+r)^n / [(1+r)^n−1]. Extra payment payoff simulates month-by-month balance reduction. Interest savings = standard total interest − accelerated total interest.
For the 2025–2026 academic year, undergraduate Direct Subsidized and Unsubsidized loans carry a 6.53% fixed rate. Graduate Unsubsidized loans are 8.08%, and Direct PLUS loans are 9.08%. Rates are set annually by Congress based on 10-year Treasury yields.
IDR plans cap monthly payments at 5–20% of your discretionary income and forgive remaining balances after 10–25 years. The SAVE plan (newest) caps undergraduate loan payments at 5% of discretionary income. Use this calculator for standard repayment; IDR amounts depend on your income.
If your loan rate is below ~6–7%, investing extra cash in a diversified portfolio may produce better long-term returns. Above that rate, extra loan payments are a guaranteed risk-free return equal to the interest rate. Pay off private loans with high rates first.
Disclaimer: Calculations are for informational purposes only and do not constitute professional financial advice. Please consult with a certified professional before making financial decisions.