Student Loan Payoff Calculator (Extra Payments)
See how extra monthly payments cut years and interest off your student loans.
What this calculates
Federal student loans default to 10-year standard amortization. Every extra dollar past the minimum goes 100% to principal, snowballing interest savings. This calculator shows how an extra monthly amount changes payoff time and total interest paid.
Formula & how it works
Standard payment from balance, rate, term. With extra: payoff_months = ln(P/(P − r×B)) / ln(1+r), where P = total monthly payment, r = monthly rate, B = balance.
Worked example
$45,000 at 6.5%, 10 yr standard = $511/mo. Add $200 extra/mo → paid off in 6.7 yr, saves $5,800 interest.
Frequently asked questions
Refinance first?
If you have stable income and no need for federal protections (PSLF, IDR), refinancing 1-2% lower beats extra payments. Federal protections lost permanently.
Avalanche or snowball?
Highest-rate first (avalanche) saves the most money. Smallest balance first (snowball) builds momentum. With multiple loans, target the highest rate.
Pay off vs invest?
If loan rate > expected investment return (~7%), pay off. If lower, split — long-term market usually wins.
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