Loan & Mortgage Repayment Calculator — Monthly Payment & Amortization

Calculate your monthly repayments, total interest paid, and view a full amortization schedule. Private by design—everything runs locally in your browser.

Inputs

Enter a positive number of years or months.

Results

Enter your loan details and click Calculate. Results will appear here.

Understanding Loan & Mortgage Repayments

Buying a home or taking out a loan can feel overwhelming because the numbers are big and the timelines are long. This mortgage repayment calculator makes the process easier by estimating your monthly payment, total interest, and how your balance changes over time. It is a practical tool for comparing loan offers, planning a budget, or seeing how a different interest rate or term affects what you pay.

At a high level, a mortgage or fixed-rate loan is repaid through regular monthly payments. Each payment includes two parts: interest (the cost of borrowing) and principal (the amount that reduces your balance). Early payments are mostly interest, while later payments apply more toward principal. This shifting balance is captured in an amortization schedule, which shows how your loan changes month by month.

How to Use the Calculator

  1. Enter the loan amount (the principal you plan to borrow).
  2. Add the annual interest rate, also known as APR.
  3. Choose the loan term in years (such as 15 or 30 years).
  4. Select your currency for display, then click calculate.
  5. Review your monthly payment, total interest, and amortization schedule.

Example: If you borrow $300,000 at a 6% annual interest rate for 30 years, your payment is a little under $1,800 per month. Over the life of the loan, the total interest can exceed the original amount borrowed. If you shorten the term to 15 years, the monthly payment goes up, but you pay far less interest overall. This is why mortgage calculators are useful for side-by-side comparisons before you commit.

Key Inputs Explained

  • Loan Amount: The principal sum of money you are borrowing.
  • Annual Interest Rate (% APR): The yearly rate charged on the outstanding balance.
  • Loan Term: The length of time you will repay the loan, usually in years.
  • Currency: Display preference only; the math is identical for any currency.

Key Outputs Explained

  • Monthly Repayment: The fixed amount you pay each month (principal + interest).
  • Total Interest Paid: The cumulative interest cost over the loan term.
  • Total Amount Paid: The sum of principal and interest across all payments.
  • Amortization Schedule: A month-by-month breakdown of principal and interest.

How This Tool Works

This calculator uses the standard fixed-rate loan amortization formula:

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

  • \(P\) = Loan principal
  • \(i\) = Monthly interest rate (annual rate / 12 / 100)
  • \(n\) = Total number of monthly payments

All calculations are performed client-side in your browser for complete privacy.

5 Fun Facts about Mortgage Repayments

Early years are mostly interest

On a 30-year fixed, month one is often 70%+ interest; by mid-term, the principal share finally overtakes interest.

Front-loaded

One extra yearly is a time warp

Making one extra full payment per year can cut ~4–5 years off many mortgages and save tens of thousands in interest.

Prepay power

Biweekly ≈ 13 payments

26 half-payments a year equals 13 full payments—an automatic prepayment that accelerates payoff without changing the rate.

Timing hack

APR vs effective cost

Quoted APR is simple; interest accrues daily between payments. Effective cost is higher due to compounding.

Real cost

Refi break-even is quick math

Divide refi costs by monthly savings to get break-even months—an easy sanity check before refinancing.

Refi check

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