How is a student loan amortization schedule calculated?

Each month, interest is charged on the remaining balance at the monthly rate (annual rate ÷ 12). The rest of your fixed payment reduces the principal. As the balance falls, less of each payment goes to interest and more goes to principal, until the balance reaches zero at the end of the term.

How much interest will I pay on a $30,000 student loan?

At 6% over a standard 10-year term, a $30,000 balance costs about $9,967 in total interest, with a monthly payment near $333. A longer term lowers the monthly payment but raises total interest paid, since more months accrue interest on a slower-shrinking balance.

Does extra payment go straight to principal?

On most federal and private student loans, yes — extra payments are applied to principal by default, but you may need to specifically request it in writing or through your servicer's portal, since some servicers apply extra payment to future installments instead unless told otherwise.

Why is my first payment mostly interest?

Interest is calculated on the full starting balance, which is at its highest point on day one. As the balance shrinks with each payment, the interest charge shrinks too, so a growing share of every fixed payment goes toward principal over time.

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Student Loan Amortization Calculator

Full payment schedule — principal, interest, and balance for every month.

Student Loan Amortization Calculator

Full payment schedule — principal, interest, and balance for every month.

Input Parameters

Your Student Loan

Loan Balance

Interest Rate (%)

Federal Direct rates reset each July 1 — check studentaid.gov for the current year's rate

Repayment Term (Years)

Standard federal plan is 10 years; extended and income-driven plans run longer

Student Loan Amortization Calculator: See Every Payment

This student loan amortization calculator builds the full month-by-month payment schedule for a fixed-rate student loan: how much of each payment goes to interest, how much reduces the balance, and what you owe after every payment until the loan hits zero.

Worked example: a $30,000 balance at 6% for a standard 10-year term produces a monthly payment of $333.06 and $9,967.38 of total interest over the life of the loan. The very first payment splits into $150.00 of interest and $183.06 of principal — that split shifts toward principal every month as the balance shrinks.

Already paying and just want the full history laid out for tax or budgeting purposes? This tool gives you the complete table. If you're deciding how to pay it off faster, the Loan Payoff Calculator models extra payments and lump sums against this same balance. Juggling several federal loans? The Student Loan Consolidation Calculator shows what combining them into one payment would actually cost.

How the Amortization Schedule Is Calculated

Student loans amortize the same way any fixed-rate installment loan does. The CFPB explains the standard formula used across federal and most private student loans:

M = P × [r(1+r)^n] / [(1+r)^n − 1]

M — fixed monthly payment
P — starting balance
r — monthly interest rate (annual rate ÷ 12)
n — total number of monthly payments (years × 12)

Each month, interest is charged on the remaining balance first (balance × r), and whatever is left of the fixed payment reduces principal. Because the balance falls every month, the interest charge shrinks and the principal portion grows — the schedule this calculator generates shows that shift row by row.

Federal vs. Private Student Loan Amortization

The math shown here applies equally to federal Direct Loans and private student loans once you're in standard repayment — both amortize on a fixed schedule at a fixed rate. The differences that matter show up around the edges: federal loans accrue simple daily interest and offer income-driven plans that this straight-line amortization doesn't model, while private loans may carry variable rates that change the monthly payment over time. For a rate that resets, re-run the calculator with the new rate from the point it changes forward — the remaining balance becomes your new starting principal.

If you're on an income-driven repayment plan rather than standard amortization, your payment is set by income and family size instead of the formula above, and you may see the balance grow before it shrinks. This calculator is built for fixed-payment, fixed-rate amortization — standard, graduated (in its early flat-payment phase), and most refinanced private loans all fit that model.