Student Loan Payment Calculator

You're holding a $42,000 federal loan offer at 6.8% interest with a 10-year standard repayment term. Monthly payment is around $483. Total interest paid over the life of the loan? About $15,990. Numbers like that change the conversation about whether to take the offer.

Feed in principal, rate, and term to get monthly payment, total interest, and total paid. Adjust the term to compare aggressive (5-year) versus standard (10-year) versus extended (20-year) repayment — longer terms mean lower monthly payments and dramatically more total interest.

For income-driven repayment plans the math is different and depends on your AGI; this tool covers fixed-payment scenarios, which is where most borrowers start.

The amortization formula behind the calculator is the standard fixed-payment one: M = P × [r(1+r)^n] / [(1+r)^n − 1], where M is the monthly payment, P is the principal, r is the monthly interest rate (annual rate divided by 12), and n is the number of monthly payments (term in years × 12). For a $42,000 loan at 6.8% over 10 years: r = 0.0068/12 ≈ 0.005667, n = 120, and the formula spits out about $483 per month. Across 120 payments that's $57,960 paid for $42,000 borrowed — $15,960 in interest, almost 38% of the original principal.

A worked example showing why term matters so much: same $42,000 loan at 6.8%, but 20 years instead of 10. Monthly payment drops to $321 — a $162-per-month relief. Total interest paid over 20 years balloons to $35,000. You paid $19,000 more in interest to spread the payments out. That tradeoff sounds obviously bad on paper, but during years when other obligations are tight, the lower monthly payment is what lets you keep paying at all. The 20-year is sometimes the right pick; just see the cost in advance.

What the calculator doesn't model: income-driven repayment plans (IDR). Federal IDR plans cap monthly payment at a percentage of discretionary income, sometimes lower than the standard amortized payment. After 20–25 years, remaining balance can be forgiven. The math is fundamentally different and depends on your income trajectory, family size, AGI, and which plan variant. For IDR projections, use the federal student aid simulator rather than this tool, which assumes a fixed-term standard repayment.

A pragmatic point on extra payments: extra principal applied early in the loan saves dramatically more interest than the same amount applied late. A $200 extra payment in month 6 of a 10-year loan saves roughly $130 in lifetime interest; the same payment in month 100 saves only about $5. The mechanism is compounding — every dollar of principal eliminated stops accruing interest for the remaining loan life. If you get a windfall, throwing it at the loan early multiplies its effect.