Mortgage Repayment Calculator

How to Calculate Mortgage Repayments

Enter your loan amount, interest rate and loan term above and this tool instantly works out your weekly, fortnightly or monthly home loan repayment, your total interest over the life of the loan, and a year-by-year chart of your remaining balance.

The Formula Behind the Calculation

Home loans use an amortization formula: each repayment is split between interest (charged on your current balance) and principal (which reduces what you owe). Because the interest portion shrinks as your balance shrinks, the repayment amount itself stays fixed for the life of the loan, but more of each dollar goes toward the principal over time — which is why the balance chart above curves rather than falls in a straight line.

Worked Example

A $500,000 loan at 6% p.a. over 30 years comes to a monthly repayment of about $2,998. Over the full term you'd repay roughly $1,079,200 in total — meaning around 54% of everything you pay back is interest, not principal.

Frequently Asked Questions

How do I calculate mortgage repayments?

Enter your loan amount, interest rate and loan term above, and your repayment is calculated instantly using the standard amortization formula banks use: payment = P × r ÷ (1 − (1 + r)⁻ⁿ), where P is the loan amount, r is the interest rate per period, and n is the total number of payments.

How is a mortgage repayment calculator different for Australia?

The maths is the same worldwide, but this calculator lets you choose weekly, fortnightly or monthly repayments — the three frequencies Australian lenders commonly offer — and displays amounts in AUD.

What does the mortgage repayment graph show?

The loan balance chart plots how much you still owe at the end of each year of your loan term. It starts at your full loan amount and curves down to zero — note that balance drops slowly at first (most of each early repayment goes to interest) and much faster in the final years.

Are weekly, fortnightly or monthly repayments cheaper overall?

More frequent repayments (weekly or fortnightly) chip away at your balance slightly faster than monthly repayments at the same annual rate, which can shave a small amount off your total interest — the repayment-by-frequency comparison above shows the difference for your own numbers.

How much of my repayment goes to interest?

Early in a loan, most of each repayment is interest and only a small part reduces the principal — the principal-vs-interest bar above shows the split over the full life of your loan for the figures you entered.

Is this calculator accurate for my actual home loan?

It gives a close estimate using a standard fixed-rate amortization schedule. Your real repayments may differ slightly due to lender fees, an introductory or variable rate that changes over time, offset accounts, or extra repayments — for those, use our Extra Mortgage Repayment Calculator and Mortgage Offset Calculator.