Student Loan Calculator
Estimate your student loan monthly payment, total interest and repayment, and how much an extra payment could save.
How to Use
- Enter the loan principal, its annual interest rate, and the repayment term in years.
- Enter any extra amount you could add to your monthly payment — leave it at $0 to see just the standard schedule.
- The result shows your standard monthly payment, total interest and total repayment, plus the payoff time, total interest, and time/interest saved with the extra payment applied.
Formula
- Monthly payment
- payment = principal × monthly_rate ÷ (1 − (1 + monthly_rate)^−months)
- With extra payment
- each month: interest = balance × monthly_rate; balance −= (payment + extra − interest), capped at what's owed
Worked Example
A $30,000 loan at 5.5% over a 10-year term, with a $50/month extra payment.
- Monthly rate: 5.5 ÷ 100 ÷ 12 ≈ 0.004583
- Monthly payment: $30,000 × 0.004583 ÷ (1 − 1.004583⁻¹²⁰) ≈ $325.58
- Standard schedule: 120 months, $9,069.46 total interest
- With an extra $50/month: 100 months, $7,441.47 total interest
- Time saved: 20 months. Interest saved: $1,627.99.
Result: Monthly payment: $325.58 / Total interest: $9,069.46 / Total repayment: $39,069.46 / Payoff time with the extra payment: 100 months (8.33 years) / Time saved: 20 months (1.67 years) / Interest saved: $1,627.99
About This Tool
What this tool does
This calculator finds the standard fixed monthly payment on a student loan from its principal, rate and term, then — if you enter an extra monthly amount — simulates the same loan with that extra payment applied, showing how much time and interest it saves.
When to use it
Use it to estimate a standard payment on a loan you're considering or already have, or to see the concrete effect of adding extra money toward a specific loan each month.
What the result means
Total interest is money paid on top of what you borrowed — the clearest figure for seeing what a longer term or higher rate actually costs. The extra-payment section shows time and interest saved on the exact same loan, so it's a direct measure of what that extra money buys you.
Assumptions & limitations
This calculator is deliberately generic: it treats any student loan as a plain fixed-rate installment loan, and does not encode any specific government loan program's interest rates, subsidized/unsubsidized accrual rules, income-driven repayment formulas, or forgiveness programs — those vary by program, change over policy cycles, and would go stale or mislead if hard-coded here. Enter the actual rate and term from your specific loan or loan offer. This tool assumes a fixed rate for the full term and that extra payments are applied to principal with no prepayment penalty (most student loans don't charge one, but confirm with your servicer). This is an estimate, not financial aid or loan advice.