Loan Repayment Calculator

A premium, interactive payoff model: drag the timeline, inspect any month, and visualize how principal and interest evolve. This uses simplified fixed-rate amortization math for learning and scenario comparison.

For educational purposes only. This calculator provides general estimates and does not provide financial, trading, tax, or legal advice.

Runs locally in your browser. No account. No signups.

Principal balance (amount borrowed).
Converted to a monthly rate as APR ÷ 12 in this model.
Converted to months (years × 12) for the amortization schedule.
Modeled as additional principal each month (illustrative).

Month Inspector

What’s happening in the month you’re viewing.
Mode: Base
Balance (this month)
—
Payment
—
Principal (this month)
—
Interest (this month)
—
Cumulative interest
—
Remaining months (est.)
—
Tip: the early months usually skew toward interest. Over time, principal share grows as the balance shrinks.

Key Results

Updates live as you type or scrub.
Payoff: —
Monthly payment (base)
—
Standard amortization payment (estimate).
Monthly payment (with extra)
—
Base payment + extra monthly (if any).
Total interest (base)
—
Sum of modeled interest (estimate).
Interest saved (extra)
—
Base interest minus extra-mode interest.

Payoff Timeline

Hover the curve or drag the timeline scrubber to inspect any month.
Month: — Drag to inspect any month

Payment Composition

Stacked area over time: principal vs interest per payment.
Hover the area to see the month’s principal/interest split.
Educational estimates only. This loan calculator performs arithmetic projections based on user-entered values and simplified assumptions (such as loan amount, interest rate, term length, and payment schedule). It does not provide personalized financial, lending, credit, tax, or legal advice, and it does not account for lender-specific underwriting criteria, variable or promotional rates, origination fees, compounding differences, payment timing, late fees, prepayment penalties, or individual credit qualifications. Results are illustrative estimates — not loan offers, approvals, or guarantees. Calculations run locally in your browser. Verify terms and costs with official lender disclosures before making decisions. See Disclaimer, Privacy Policy, and Terms of Use.

How Loan Payments Work

Most fixed-rate loans use amortization: each monthly payment includes interest (the cost of borrowing) and principal (paying down the balance). Early payments often include more interest because the balance is higher. As the balance declines, the interest portion typically declines too (in this simplified model).

What Drives Your Payment and Total Cost

  • Loan amount: larger balances generally increase payments and total interest.
  • APR: higher rates generally increase both the monthly payment and modeled lifetime interest cost.
  • Term length: longer terms often reduce the monthly payment but can increase total interest paid.

Extra Payments

In a simplified amortization model, extra payments applied to principal can reduce interest because they reduce the balance earlier. Real loans can have rules (fees, prepayment terms, timing conventions) that change the outcome.

For related tools, explore the Mortgage Calculator, Savings Goal Calculator, and Investment Calculator.

Loan Calculator FAQ

Does this calculator store my data?

No. The calculator runs locally in your browser. Inputs are not stored by FinFormulas.

Is the result exact?

No. Results are estimates based on the numbers you enter and simplified assumptions. Real loans can include fees, insurance, taxes, and different payment schedules.

Do extra payments always save interest?

In this simplified model, extra principal payments usually reduce interest by reducing the balance earlier. Real loan rules can change the result.

Will this tell me what I should do?

No. This tool provides arithmetic outputs from your inputs so you can compare scenarios. It does not provide individualized guidance or recommendations.

Reviewed & Updated

Calculator logic and on-page content reviewed for clarity and educational accuracy. Last review: December 2025.