Student Loan Payoff Calculator

Student loan payoff timeline calculates how long it takes to pay off a student loan balance at a given monthly payment, and what the total interest paid will be over the life of the loan.

Core amortization formula: M = P × [r(1+r)^n] ÷ [(1+r)^n − 1] Months to Payoff (custom payment) = −ln(1 − P×r÷M) ÷ ln(1+r) Total Interest = (M × n) − P

Where:

• M = monthly payment
• P = principal balance
• r = monthly interest rate (annual rate ÷ 12)
• n = number of months

What each variable means:

• Principal (P) is your current outstanding balance, not the amount originally borrowed. If you have been paying for a while, the difference is substantial.
• Interest Rate: federal student loan rates for 2024–2025 were 6.53% for undergraduate subsidized and unsubsidized, 8.08% for graduate, and 9.08% for PLUS loans. Private loans run 4–14% depending on credit.
• Monthly Payment (M) is the required standard payment, or whatever larger figure you actually send.
• Extra payment impact: even $50–$100 a month cuts both the total interest and the payoff date sharply.

Federal repayment plans and terms:

Worked example: Loan balance: $32,000 at 6.53% interest. Standard 10-year repayment.

r = 6.53% ÷ 12 = 0.5442% = 0.005442 n = 120 months M = 32,000 × [0.005442 × (1.005442)^120] ÷ [(1.005442)^120 − 1] (1.005442)^120 = 1.9179 M = 32,000 × [0.005442 × 1.9179] ÷ [0.9179] = 32,000 × 0.011370 = $363.84/month

Total paid = $363.84 × 120 = $43,661 Total interest = $43,661 − $32,000 = $11,661 in interest

With $100 extra/month ($463.84): New payoff = 87 months (7 years 3 months). Interest saved = $3,433.

One wrinkle if you type those numbers in above: the exact payment is $363.8446, and $363.84 is a fraction of a cent short of it every month. The calculator reports 121 months rather than 120 for that reason, with a final payment of a few dollars. That is not an error in either place, it is what rounding a payment down actually does, and real servicers handle it the same way.

Look at what that extra $100 buys. It is 27% more money per month, and it removes 33 months of payments and a third of the interest. The reason is that every extra dollar goes straight to principal, so it never accrues interest again for the remaining life of the loan. Early extra payments are worth far more than late ones for the same reason, which is why the standard advice is to throw any windfall at the loan in year one rather than year eight.

This page starts from a payment you already make and tells you when the loan ends. To go the other way, from a term to the payment it implies, use the student loan repayment calculator. It also lines up the 10, 15, 20 and 25-year plans side by side and prices what refinancing a point lower would save.