Orbit
HomeDealsBlog
Resources
ToolsCancel HubSubscription DealsCompareNews
Get Started →
Home loan calculator

Mortgage Repayment Calculator Australia

Work out your home loan repayments monthly, fortnightly or weekly, and see the total interest over the life of the loan. Free, no signup.

Free, no signupMonthly, fortnightly or weeklyTotal interest shown
Your home loan
How much you're borrowing
$
Your annual rate (% p.a.)
%
Most Australian home loans run 25 to 30 years
yrs
Your repayment
$3,597.30/month
Principal & interest repayment over 30 years$695,029 total interest
10y20y30y
Principal & interest: the balance falls to zero over the term.
Repayment per month$3,597.30
Number of repayments360
Total interest$695,029
Total repaidPrincipal plus interest over the full term$1,295,029
Repayment by frequency
FrequencyRepaymentTotal interest
monthly$3,597.30$695,029
fortnightly$1,659.50$694,408
weekly$829.58$694,142
Each frequency is worked out on its own true period, so fortnightly is not the monthly figure halved.
Want to clear it sooner?
Paying half your monthly amount every fortnight squeezes in an extra month of repayments each year, which can cut years off the loan. See the effect with the mortgage overpayment calculator.
Estimate only. Assumes a fixed rate for the full term and excludes fees, offset accounts and rate changes. A guide, not financial advice.
Simon Chadwick
Simon Chadwick
Founder, Orbit Money
Method: standard amortisation formulaUpdated: 15 July 2026Sources: Moneysmart

How your mortgage repayment is worked out

A principal and interest home loan uses the standard amortisation formula. Each repayment covers the interest charged on the balance for that period, and whatever is left over reduces the principal. Because the balance shrinks over time, the interest portion of each repayment falls and the principal portion rises. The formula that ties it together is repayment = P × r ÷ (1 − (1 + r)−n), where P is the loan amount, r is the interest rate for a single period, and n is the total number of repayments. This calculator applies it for monthly, fortnightly and weekly repayments.

Monthly, fortnightly or weekly repayments

The frequency you choose changes the size of each repayment, not the maths behind it. A fortnightly repayment is worked out on a true fortnightly period, with 26 repayments a year, so it is not the monthly figure halved. Over the same term, the three frequencies cost close to the same in total interest. The popular saving comes from paying half of your monthly repayment every fortnight: that adds up to the equivalent of 13 monthly repayments a year, which pays the loan down faster. The comparison table above shows all three side by side.

Interest-only vs principal and interest

Principal and interest repayments pay down the loan so it clears by the end of the term. Interest-only repayments cover just the interest, so the balance holds steady and the full loan is still owing when the interest-only period ends. The repayments are lower while they last, which suits some investors, but you pay more interest overall because the balance never falls. Toggle between the two above to see the gap for your own loan.

A worked example

Take a $600,000 loan at 6% p.a. over 30 years, paid monthly. The period rate is 6% ÷ 12 = 0.5%, over 360 repayments, which gives a repayment of about $3,597 a month. Across the full term that adds up to roughly $1,295,000 repaid, of which around $695,000 is interest, more than the amount borrowed. Shorten the term or lower the rate and the total interest drops sharply, which is why the term and rate matter as much as the loan amount.

Frequently asked questions

How are mortgage repayments calculated?
A principal and interest repayment uses the standard amortisation formula: repayment = P × r ÷ (1 − (1 + r)^−n), where P is the loan amount, r is the interest rate for one period, and n is the total number of repayments. Interest is charged on the balance still owing, so early repayments are mostly interest and later ones are mostly principal. This calculator applies that formula for you and shows the total interest over the full term.
Are fortnightly repayments better than monthly?
It depends on how the fortnightly amount is set. Worked out fairly, a true fortnightly repayment over the same term costs about the same as monthly because there are 26 fortnights and 12 months in a year. The saving comes from a common trick: pay exactly half your monthly repayment every fortnight. That squeezes in the equivalent of 13 monthly payments a year instead of 12, so the loan clears earlier and you pay less interest.
What is the difference between interest-only and principal and interest?
Principal and interest repayments pay down the loan, so the balance falls to zero by the end of the term. Interest-only repayments cover just the interest, so the balance does not move and the full amount is still owed when the interest-only period ends. Interest-only repayments are lower month to month, but you pay more interest overall because the balance never shrinks. Switch between the two above to compare.
How much interest will I pay over the life of the loan?
On a $600,000 loan at 6% p.a. over 30 years, principal and interest repayments come to about $3,597 a month and roughly $695,000 in total interest, more than the amount borrowed. The total interest depends heavily on the rate and the term: a shorter term means higher repayments but far less interest. The calculator shows your total interest and total repaid as soon as you enter your figures.
Do extra repayments reduce my mortgage?
Yes. Any repayment above the required amount comes straight off the principal, so every future interest charge is calculated on a smaller balance. Even small regular extra repayments can cut years off the loan and save a large amount of interest. Many Australian lenders allow unlimited extra repayments on variable-rate loans, though fixed-rate loans often cap them, so check your loan terms.

Related tools

Mortgage Overpayment Calculator
See how extra repayments cut your interest and clear the loan sooner.
Stamp Duty Calculator
Estimate the transfer duty on your property purchase by state.
Land Tax Calculator
Work out the annual land tax on an investment property.
Budget Calculator
Check how the repayment fits your monthly budget.

Your mortgage is the big one. The small drains add up too.

Orbit finds every subscription and recurring charge leaving your account and puts them in one place, so more of your money goes on the home loan.

Try Orbit free
Simon Chadwick
About the author
Simon Chadwick
Founder of Orbit Money

Simon is the founder of Orbit Money, a tool that helps people track subscriptions and recurring spend. He builds Orbit's free money calculators and writes about personal finance for Australian and UK readers.

More from Simon →
This tool is a guide, not financial advice.