savingcalculators

Student Loan Calculator: Payoff & Interest

Use this student loan calculator to find your exact monthly payment, payoff date, and total interest. Works as a student loan payoff calculator for both federal and private loans.

$
%
$
Months to pay off—
Payoff timeline—
Total interest paid$0
Total amount paid$0
Advertisement  ·  728 × 90

How this calculator works

The number of months to pay off is calculated from the standard loan payoff formula:

n = −log(1 − rP/M) ÷ log(1 + r)

  • n = number of monthly payments
  • r = monthly interest rate (annual rate ÷ 12 ÷ 100)
  • P = current loan balance (principal)
  • M = monthly payment amount

The final payment is typically smaller than a full payment. Total interest is calculated as (sum of all payments) − original balance.

Federal student loan interest rates for 2024–25: 6.53% for undergrad Direct Loans, 8.08% for graduate Direct Loans, 9.08% for PLUS Loans. Private loan rates vary from approximately 4% to 17% depending on credit score and lender.

Source: Federal loan interest rates per US Department of Education — StudentAid.gov. Payoff formula per standard amortization mathematics.

FAQ

What is the fastest way to pay off student loans?
Pay more than the minimum every month — even an extra $50–100/month cuts years off. Pay highest-interest loans first. Avoid income-driven repayment unless pursuing Public Service Loan Forgiveness (PSLF), as these plans maximize total interest.
Should I refinance my student loans?
Refinancing can lower your rate, but refinancing federal to private removes all federal protections — income-driven repayment, deferment, forbearance, and forgiveness. Only do it if you have stable income and no plans to pursue forgiveness.
What happens if I only pay the minimum?
On a $30,000 loan at 6.5%, the standard 10-year repayment costs ~$10,600 in interest. Extending to 20 years nearly doubles total interest paid while only halving the monthly payment. Always run both scenarios in this calculator before choosing a repayment plan.
How is the monthly student loan payment calculated?
Standard amortization: PMT = balance × r / (1 − (1+r)−n), where r is the monthly rate and n is months. A $30,000 loan at 6.5% APR over 10 years (120 months) gives PMT = $340.69/month, total paid $40,883, total interest $10,883.
Should I pay off student loans early or invest the money?
Math: if your loan rate is below 5-6% (after-tax), invest; if above, pay down. The S&P real return is ~7%, so a 4% loan loses to investing. But debt payoff is a guaranteed return; investing isn't. Federal loans also have flexible repayment options that change the math.
Should I refinance my student loans?
Federal loans: only if the new rate beats yours by 2+ points AND you will never need federal benefits (income-driven repayment, PSLF forgiveness, deferment, forbearance). Refinancing federal to private permanently forfeits those protections. Private loans: refinance whenever a better rate appears.
Advertisement  ·  728 × 90

Related calculators

Learn more on the blog

Advertisement  ·  responsive horizontal