Free · Australian Home Buyers & Investors
Enter your property price, deposit, interest rate, and loan term to instantly see monthly, fortnightly and weekly repayments — plus total interest paid and your LVR.
Monthly repayment
$3,694.30
$600,000
Loan amount
80.0%
LVR
$1,329,949
Total repayments
$729,949
Total interest
All frequencies
Estimates are for principal & interest only. Does not include lender fees, LMI, offset accounts, or redraw facilities. Always confirm with your lender or mortgage broker.
A mortgage repayment calculator uses the amortisation formula to work out how much you owe each period. Every repayment covers two things: interest charged on the outstanding balance, and a principal reduction that slowly pays down what you borrowed. Understanding how this works helps you make better decisions about loan term, repayment frequency, and extra repayments.
Lenders use the following formula to calculate your fixed repayment amount. The key insight is that the repayment is constant — but the split between interest and principal shifts over time. Early repayments are mostly interest; later repayments are mostly principal.
Formula
M = P × [r × (1 + r)ⁿ] ÷ [(1 + r)ⁿ − 1]
P = loan principal · r = monthly interest rate (annual rate ÷ 12) · n = total monthly payments (years × 12)
Worked example
You buy a property for $700,000 with a $140,000 deposit (20%), leaving a $560,000 loan at 6.5% per annum over 30 years.
On this loan, you pay more in interest than the original loan amount. This is why reducing your rate by even 0.5% or shortening the term by 5 years makes a significant difference to the total cost.
Switching from monthly to fortnightly payments is one of the most effective ways to reduce total interest without refinancing. The reason: there are 26 fortnights in a year, so you make the equivalent of 13 monthly payments instead of 12. That extra month of principal reduction per year compounds significantly over a 30-year term.
Fortnightly payment approach
Fortnightly payment = Monthly repayment ÷ 2
This simple division results in 26 payments × half-monthly amount = 13 full monthly payments per year, not 12.
Worked example — same $560,000 loan
Using the same $560,000 loan at 6.5% over 30 years, compare monthly vs fortnightly repayments.
Fortnightly repayments save nearly 4 years and $68,000 in interest with no change to rate or loan structure — just payment frequency. The same logic applies to weekly payments.
Use this mortgage calculator alongside the stamp duty calculator to understand your total upfront costs, and the borrowing power calculator to check how much you can borrow before you start searching.
If you are buying an investment property, the rental yield calculator and cash flow calculator help you model returns alongside your financing costs.
Australian mortgage repayments use the standard amortisation formula: M = P × [r(1+r)ⁿ] ÷ [(1+r)ⁿ − 1], where P is the loan principal, r is the monthly interest rate (annual rate ÷ 12), and n is the total number of monthly payments (years × 12). Each repayment covers the interest accrued that month plus a portion of principal — in the early years most of the payment is interest, and the principal portion grows over time.
LVR (Loan-to-Value Ratio) is your loan amount divided by the property value, expressed as a percentage. A $560,000 loan on a $700,000 property is an 80% LVR. Lenders typically require Lenders Mortgage Insurance (LMI) on loans above 80% LVR, adding thousands to your upfront costs. Keeping LVR at or below 80% avoids LMI and often unlocks better interest rates.
Lenders Mortgage Insurance (LMI) is insurance that protects the lender — not you — if you default on a loan with an LVR above 80%. On a $700,000 property with a 10% deposit ($70,000), the $630,000 loan is at 90% LVR and LMI typically costs $12,000–$18,000 depending on lender and loan size. LMI can usually be capitalised (added to the loan), but this increases total interest paid over the life of the loan.
Paying fortnightly reduces total interest because you make 26 half-monthly payments per year — equivalent to 13 full monthly payments rather than 12. On a $560,000 loan at 6.5% over 30 years, switching from monthly to fortnightly payments can save approximately $68,000 in interest and cut nearly 4 years from the loan term. Weekly payments produce a similar effect.
A fixed-rate mortgage locks in an interest rate for a set period (typically 1–5 years in Australia), providing repayment certainty regardless of RBA rate moves. A variable rate moves with the lender's standard variable rate, which tracks the RBA cash rate. Variable loans often allow unlimited extra repayments and offset accounts; fixed loans usually cap extra repayments at $10,000–$20,000 per year and may not allow offset accounts.
On a $560,000 loan at 6.5%, a 30-year term costs approximately $714,000 in total interest. The same loan over 25 years costs approximately $572,000 in interest — a saving of $142,000. The monthly repayment increases by around $240 per month, but the total saving over the life of the loan is substantial.