Student Loan Payoff Calculator
Calculate student loan payoff timeline and total interest from balance, interest rate, and term.
Compare standard and accelerated payment strategies.
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) — your current outstanding loan balance, not the original borrowed amount. If you’ve been making payments, use the current balance.
- Interest Rate — federal student loan rates for 2024–2025: undergraduate subsidized/unsubsidized: 6.53%; graduate: 8.08%; PLUS loans: 9.08%. Private loans: 4–14% depending on credit.
- Monthly Payment (M) — the required standard payment or any extra amount above the minimum.
- Extra payment impact — paying even $50–$100 extra per month dramatically reduces total interest and payoff time.
Federal repayment plans and terms:
| Plan | Term | Best For |
|---|---|---|
| Standard | 10 years | Lowest total interest |
| Graduated | 10 years (rising payments) | Expect income growth |
| Extended | 25 years | Lower payments now |
| IBR / SAVE | 20–25 years (income-based) | Low income, PSLF path |
| PSLF | 10 years (nonprofit/gov employees) | Full forgiveness after 120 payments |
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.
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.
How we build and check this calculator
This calculator runs entirely in your browser, so the numbers you enter stay on your device. The math behind it is written by hand and tested against worked examples and standard references before the page goes live.
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