Wondering if an offset account is worth it? Let’s find out.
If you’ve ever wondered whether setting up an offset mortgage account could help you save money, reduce interest, or pay off your loan faster, you’re in the right place.
This free calculator lets you model how an offset account, combined with your savings and everyday spending, can impact your mortgage. Even if you don’t currently use an offset account or understand exactly how they work, this tool will walk you through the basics and show you what’s possible.
It’s simple, beginner-friendly, and built to help you make a smarter decision about your mortgage.
What This Tool Helps You Discover
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How much interest an offset account would save you
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How a credit card can help keep more money in your offset
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How much interest you could save over time
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How many years you could shave off your loan
No jargon. No spreadsheet formulas. Just your real numbers and a clearer picture.
Try the Offset Mortgage Calculator
Use the tool below to enter your emergency fund, planned annual savings, and monthly spending. You’ll also have the option to factor in a credit card strategy, add your mortgage portions, and then run the calculation.
The calculator runs in your browser. No sign-up or personal data required.
What Is an Offset Account?
An offset account is a type of bank account that’s linked to your mortgage. Instead of earning interest like a regular savings account, your balance is “offset” against your home loan.
So if you have a $400,000 mortgage and $30,000 in your offset account, your bank only charges interest on $370,000.
This simple difference can result in thousands of dollars saved over the life of your loan. And because mortgage interest is calculated daily, even small balances in your offset account can make a meaningful impact, especially over time.
Offset accounts are commonly available in countries like New Zealand, Australia, and the UK. Some come with fees or slightly higher interest rates, which is why it’s important to calculate whether the benefits outweigh the cost.
What banks offer an offset account in NZ?
Currently, here are the banks that offer an offset account or a revolving credit facility (which works in a very similar way):
Offset accounts:
Revolving credit accounts:
What’s the Credit Card Strategy?
This tool also gives you the option to model what happens if you use a credit card to delay expenses. That might sound strange at first, but here’s why it works.
If your credit card offers 30 to 55 days interest-free, and you pay it off in full each month, you can delay spending from your bank account. That means your money stays in your offset account longer, continuing to reduce your mortgage interest while your card handles short-term expenses.
For example, if you spend $3,000 a month on your card and average 20–25 days before repayment, that’s around $2,000 sitting in your offset account that wouldn’t be there otherwise. Over a year, that adds up fast.
The key is: you must always repay your card on time and in full. If you do, there’s no downside—and it could be one of the easiest ways to accelerate your loan payoff without cutting your budget.
After You Run the Numbers
Once you enter your details, the calculator will show a side-by-side comparison:
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How much interest you pay with your current setup
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How much interest could you save with an offset strategy
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Whether using a credit card buffer adds meaningful extra savings
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How many years you might save on your mortgage term
The tool uses standard amortization formulas and your actual data, not averages or estimates, so the insights are tailored to your situation.
Helpful Resources
Do I need an offset account to use this tool?
No. This calculator is designed to help you decide whether opening one would be worthwhile based on your actual savings and mortgage structure.
What happens if I don’t use a credit card?
You can leave that section blank and still run the full offset model. The credit card strategy is optional but can enhance your savings if you use one responsibly.
Does this work in my country?
Offset accounts are common in New Zealand, Australia, the UK, and a few other markets. If your bank offers them, the strategy may apply. Check with your lender to confirm availability.
