What Happens to Your Mortgage If the RBA Raises Rates by 1%?

If the RBA raises rates and your lender passes on the full 1%, your mortgage repayment can jump by a few hundred bucks a month. Not exactly devastating in a movie-trailer way, but extremely annoying in a "there goes the buffer" way.

The useful bit is this: the maths is predictable. Once you turn a rate rise into real dollar figures, you can stop doom-scrolling rate headlines and start making decisions like a calm adult. Or at least a slightly less stressed one.

Here is what a 1% rise actually does to an Australian mortgage, why the jump often feels bigger than expected, and what to do before your lender sends you that cheerful little email.

First up: the RBA does not set your mortgage rate directly

The Reserve Bank of Australia sets the cash rate target. Your lender sets your home loan rate. When the RBA moves, banks often pass through all or most of the change to variable-rate borrowers, but they do not have to match it exactly.

So when people ask what happens if the RBA raises rates by 1%, the practical version of the question is: what happens if my home loan rate ends up 1 percentage point higher?

That is the scenario worth testing, because that is the one that hits your bank account.

What a 1% rise looks like in real dollars

Here are some worked examples using a 30-year principal-and-interest loan.

• $400,000 loan: 6.0% = about $2,398/month. 7.0% = about $2,661/month. Increase = $263/month.
• $500,000 loan: 6.0% = about $2,998/month. 7.0% = about $3,327/month. Increase = $329/month.
• $700,000 loan: 6.0% = about $4,197/month. 7.0% = about $4,657/month. Increase = $460/month.
• $900,000 loan: 6.0% = about $5,396/month. 7.0% = about $5,988/month. Increase = $592/month.

That is why a 1% move matters. It is not just a headline. It is your groceries, your savings rate, your childcare flexibility, or your ability to go one month without muttering at your internet bill.

Note: These repayment examples use the standard principal-and-interest loan amortisation formula, assuming 30 years remaining and monthly repayments.

Why the jump feels bigger than people expect

Mortgage repayments are not linear. When the interest rate rises, your repayment is recalculated over the remaining loan term at a higher cost of debt. That means the extra amount can feel surprisingly chunky, especially if:

• you borrowed recently and still have a large balance
• your loan term is still close to 30 years
• your household budget already had no slack in it
• you rolled off an older fixed rate and forgot what normal variable rates look like

In other words, rates do the most damage when your loan is still large and your optimism was doing a lot of heavy lifting.

Do banks not already test you for this?

Usually, yes. Under APRA's prudential settings, authorised deposit-taking institutions generally apply a serviceability buffer of at least 3 percentage points above the product rate for most new residential mortgage lending assessments. So a borrower applying at 6.0% is generally tested around 9.0%.

That buffer matters, but it is not magic. It helps banks check you could survive a higher rate on paper. It does not mean your actual household budget will feel fine after rent, childcare, insurance, food and whatever bizarre amount you spent at Bunnings for "one quick thing".

If you want to see how lenders think about your income and debts, the Borrowing Capacity Calculator is useful. If you want to see how your actual life feels, open your banking app and be brave.

Variable loans vs fixed loans

Variable rate borrowers

If your loan is variable, you are the one most likely to feel the change fairly quickly. Lenders often adjust rates within days or weeks of an RBA decision, although the exact timing and amount can vary.

Fixed rate borrowers

If you are fully fixed, your repayment usually stays the same during the fixed term. Lovely. Peaceful. Very 2021 energy.

The catch is what happens when the fixed period ends. You normally roll onto a revert rate or refinance. If market rates are much higher by then, the jump can still hit hard. So a 1% RBA rise may not hurt you today, but it can absolutely matter for your next rate.

How to stress-test your mortgage properly

There are two simple ways to do this:

1. Add 1% to your current rate and work out the new monthly repayment.
2. Check whether your budget still works if that extra repayment becomes permanent.

Do not just ask, "Could I survive this?" Ask, "Would I still be able to save, handle an emergency, and function like a normal person?" Surviving is a low bar for a 30-year financial commitment.

What you can do before the next move

1. Build buffer, not just bravery

Cash in an offset account can reduce interest while staying accessible. If your loan has an offset, that is often one of the cleanest ways to soften the blow of higher rates. If you do not have offset, plain savings still matter. A few months of higher repayments sitting in cash can turn panic into inconvenience.

If you want to compare how offset savings behave versus just throwing cash straight onto the loan, our Offset Mortgage Calculator is handy.

2. Check whether your rate is already a bit rubbish

Sometimes the first move is not cutting takeaway. It is checking whether your lender is quietly charging you more than the market. If another lender is meaningfully cheaper, even shaving 0.30% to 0.60% off your rate can make a future 1% rise less painful.

That is where the Refinance Calculator earns its keep. It helps you work out whether switching is actually worth the admin, rather than just emotionally satisfying.

3. Cut recurring costs before you cut joy

People usually start with coffees, streaming and tiny fun expenses. Fair enough, but bigger recurring line items often matter more: insurance, phone plans, gym memberships nobody uses, car loans, and subscriptions multiplying in the dark like gremlins.

The goal is not to become incredibly disciplined for twelve days. The goal is to create monthly breathing room that still exists in three months.

4. Keep extra repayments flexible if needed

If you are already ahead on the loan, that is great. Just make sure you understand the difference between redraw and offset, and whether your emergency cash is actually easy to access when you need it. Saving interest is good. Being cash-poor during a rough month is less good.

A quick worked example

Say you have a $650,000 mortgage over 30 years and your rate goes from 6.1% to 7.1%. Your monthly repayment would rise from roughly $3,939 to $4,368. That is about $429 extra each month, or roughly $5,151 a year.

That extra amount does not feel terrifying in spreadsheet font. It feels terrifying when it lands at the same time as council rates, school costs, and the car deciding this is its moment.

That is why doing the maths early helps. You can make calm decisions before your budget becomes a hostage negotiation.

Should you refinance before rates rise?

Maybe, but do it for the right reason. A refinance can make sense if:

• your current rate is no longer competitive
• you want a better offset or redraw setup
• cashback or lower ongoing fees improve the numbers
• the break-even point is reasonably quick

It does not make sense if the new deal looks shiny but costs more after fees, or if you are giving up features you actually use. Low rate, no offset, weird restrictions, then surprise, your "better" loan is just cheaper-looking.

The bottom line

A 1% rise in your mortgage rate is not a theoretical annoyance. For many Australian borrowers, it means an extra few hundred dollars every month. The bigger the loan and the longer the term left to run, the more it bites.

The smart move is boring but effective: run the numbers, review your rate, build a buffer, and fix weak spots before the next increase lands. Rate rises are stressful enough without adding avoidable chaos on top.

Sources

• Reserve Bank of Australia, interest rate decisions
• Reserve Bank of Australia, cash rate statistics
• APRA, housing lending standards and the 3% serviceability buffer