Student Loan Interest & Payoff Timeline Calculator

Estimate monthly payment, total interest cost, and your payoff timeline with control over extra payments and capitalization events.

▶️ Enter your inputs above then tap Calculate to view results instantly, plus export options for print or PDF summary.

Loan Balance ($)

Annual Interest Rate (%)

Repayment Term (Years)

Extra Monthly Payment ($)

One-Time Lump Sum Payment ($)

Capitalize accrued interest

Summary of Your Plan

Total Payoff Months

~-- years

Total Interest Paid

$--

Standard interest: $--

Total Savings

$--

Timeline saved: -- months

Remaining Loan Balance vs. Time

Monthly Interest vs. Principal

Amortization Schedule

The first 6 months of your loan payment schedule.

Month	Payment	Interest	Principal	Extra	New Balance

How It Works

This tool uses standard financial formulas to project your loan payoff. Here's a quick overview of the logic:

Monthly Payment (M) Calculation: For a fixed-rate loan, the formula is:

                            
                                $$ M = P \times \frac{r(1 + r)^n}{(1 + r)^n - 1} $$

Where P = principal, r = monthly rate (APR ÷ 12), n = total number of payments.

Monthly Breakdown: Each month, your payment is split between interest and principal. The interest portion is calculated as previous balance × r. The rest of the payment reduces your principal.
Extra Payments: Any extra payments you enter go directly toward reducing the principal, which in turn reduces the amount of interest you accrue over time.
Interest Capitalization: If you select this option, any unpaid interest that accrues during a grace or deferment period is added to your loan's principal before repayment begins, increasing the total amount you'll pay interest on.

FAQs (Search-Optimized & Answer-Driven)

1. How do I calculate monthly student loan interest?

Divide your APR by 365 days to get the daily rate. Multiply by your principal and the days since your last payment to see accrual.

2. What is capitalization, and how does it affect my loan?

Capitalization means unpaid interest gets added to your principal—now you're paying interest on that too. It typically occurs after reaching repayment or ending deferment/grace periods.

3. Can I pay off my student loan faster with extra payments?

Absolutely. Even modest monthly or one-time extra payments significantly reduce interest costs and shorten your payoff horizon.

4. Why do early loan payments go mostly to interest?

That’s how amortized loans work. Early payments cover mostly interest because your balance is still large, which decreases over time.

5. What happens with variable interest rates or if I refinance?

If the rate changes mid‑term or you refinance, the calculator adjusts future interest per period automatically. Just update the rate any time and recalculate.

6. How are federal vs private loans different in this calculator?

Both follow the same amortization logic, but federal loans may allow interest capitalization events and options like income-driven repayment; you can include those features in your inputs.

Build Confidence and Control Your Debt

With this Student Loan Interest & Payoff Timeline Calculator, you can compare standard vs accelerated repayment plans, test scenarios, view amortization schedules, foresee total interest paid, and share or print your results. It's a planning tool you can trust—and act on.