All calculators are downloadable Excel spreadsheets that allow you to save and amend your own personal data. With all the spreadsheets, enter your personal data in the purple coloured cells.

mortgage calculator with extra payments

Looking to see how much that mortgage will cost you? Or how much of a difference extra repayments will make? This calculator can help.


mortgage calculator with multiple interest rates

Or if you have multiple mortgages, you can use this spreadsheet below and it will add up the totals for you on the summary total mortgages tab.


how many years to pay off mortgage calculator

Looking at buying a house or increasing your monthly payments? This calculator will tell you how many years a house will take to pay off at varying house prices, interest rates and monthly payments.


Pay off the mortgage or invest calculator

This calculator allows you to compare the financial decision between paying down the mortgage or investing with any extra cash you have.

The calculator relies on you knowing your investor tax rate. Note, that if you are in a PIE fund, this rate may differ from your ordinary income tax rate.

What is more of a challenge is knowing how much tax you are paying as an investor. It is dependent on a lot of variables. Whether you are in a PIE fund or not. Whether you are invested in NZ companies or not and are benefiting from imputation credits. Whether you are in a PIE fund or not. Whether you are liable for FIF tax or not. How much your investments pay out in dividends, and so on. All that being said because this calculator can’t calculate your tax liability for you. You will need to make a best guess. In the example sheet I have used 1.4%, which is 5% of 28%. 28% being the assumed investor tax rate and 5% being the assumed taxable investment income. Your situation may differ.

From there, the calculator will tell you whether you may be better off paying off the mortgage or investing. With this decision there is much more than the financials to consider. Diversification, risk management, liquidity, timeframes, and goals are all equally important considerations. This provides a starting point.

To be honest, you do most of the work on this calculator. The calculator not doing too much calculating at all! The important part is the process you go through to get to your calculations, and that is where the calculator helps.


Offset mortgage calculator

This calculator lets you know how much interest you could save and how much faster you could pay off your home loan using an offset mortgage facility. You can also see what interest rate you are actually paying when utilising an offset mortgage.

In short, an offset mortgage is a mortgage that links your savings and cheque accounts to the mortgage, and deducts these balances from your mortgage. So, if you have a $100,000 floating offset mortgage and $60,000 in savings, you will only pay the mortgage interest on $40,000 ($100,000 mortgage minus $60,000 savings), rather than the full $100,000 mortgage.

The main downside to be aware of is that with offset mortgages you do pay the current floating mortgage rate on any money that isn’t offset. The floating rate is typically higher than you can get fixing. So ensure you don’t have significantly more money on the loan than you have (or will have shortly) in your savings and cheque accounts.

You also need to be aware that any money you have linked to an offset account is not earning additional interest. You can’t double dip. The interest savings from the mortgage alone though is usually significantly higher than your savings interest anyway.

Finally, when looking at the results it can be great to see the interest savings and time shaved off the mortgage, however just note that there is always an opportunity cost. If the money you are offsetting against is serving a purpose such as an emergency fund or was going to be sitting in savings anyway then great. But if that money could be used elsewhere instead such as investing, then just consider that trade off as part of your decision making. What are you missing out on. Also, if you weren’t using an offset mortgage at the floating rate, chances are you may be using a fixed mortgage at a lower rate, so the calculator also shows the results for the savings you would make using an offset mortgage if you were fixed at a lower rate instead.

With the calculator itself, you just enter your data in the purple cells and the results will formulate. If you want to add in additional savings to your offset account in the form of regular monthly or lump sum contributions, then enter that amount(s) in column E. If you want to withdraw/spend any of your savings, then you can just enter a negative number in column E. If you want to make actual contributions towards paying down the mortgage (rather than offsetting) then enter those amounts in column I. In column K you can see how much per month your are paying in mortgage interest once your offset savings have been deducted.

A couple more notes about offset mortgages and the calculator. Some banks may charge fees for set up or ongoing use. The rate is floating and is subject to changes.This will impact the results of the calculator.


Revolving credit mortgage calculator

Like the offset mortgage, a revolving credit mortgage attempts to pay off your home loan faster. It is basically a big overdraft where you can have your income go into, as well as your expenses come out of. The theory is that over time, as your income is hopefully higher than your expenses, the mortgage reduces faster than it would otherwise.

Some like to take advantage of this type of loan by having the overdraft as low as possible for as long as possible. For example, if you have a $50,000 revolving credit mortgage and you receive a monthly income of $7,000, then your mortgage balance is temporarily $43,000 until your spending over the month increases the mortgage balance (hopefully to less than $50,000 starting point) until your next income comes in. One way to keep the balance lower for longer, and thus minimising your mortgage payments, is to delay paying your expenses or pay as few expenses as much as possible (without paying penalties). For example, paying the mortgage weekly rather than monthly. Or using a credit card to delay paying your expenses a month or so (before any credit card fees are incurred). If we assume a $50,000 loan at 8% interest over 25 years on revolving credit, where one scenario you pay your $7,000 a month expenses weekly, and in another instance you pay your expenses monthly, you will save around $1,000 in interest payments and pay off the home loan 2 months sooner. This assumed a monthly income of $7,500. No change apart from paying your expenses weekly or monthly. $1,000 savings from just a $50,000 mortgage is not a bad return for small amount of effort. The difference can be even greater, the greater the difference between your income and spend. Paying expenses monthly working out better because the interest on your home loan is calculated daily, so the longer you can keep the balance lower, the better off you will be. This structure does require a lot of discipline from you though. You need to know your cashflow intimately and you need to be sure using a credit card doesn’t become too easy, making unnecessary purchases.

Banks often limit how much you can take out on revolving mortgage so just be aware of that. The interest rates on revolving mortgages are typically significantly higher than alternative fixed rates so make sure you are optimising the amount you have on revolving mortgage. Floating mortgage rates are subject to change (higher or lower) so there is that risk too. As such, you want to be careful mot too take out too much revolving credit, due to the higher rate. Ideally, you’d only want to put aside enough in a revolving credit mortgage that would see you better off than being in an alternative fixed mortgage. A financial Adviser can help with deciding the optimal amount.

There are two types of revolving credit mortgage. One where you pay the principal and interest as you would most other mortgages. Another where you pay interest only and rely on your balance going down over time due to higher income than spend or by selling prior to mortgage principal is due. This calculator here is the reducing principal one. I don’t encourage interest only over the long term so haven’t included that type of calculator here. But if you are interested in that let me know.

You have the option here to enter the frequency of your income and spend. You can also choose up to 3 additional lump sum payments that you may be expecting to make. If you plan to withdraw some money at some stage, you can use a negative number here too. For the one off contributions or withdrawals I have spread the amount over the course of a year, as it is unknown when exactly when in the year you will make the contribution or withdrawal. So if you receive the one off income earlier in the year then the results will be slightly better than the outcomes of the calculator, whereas if you receive the income later in the year, the results will be slightly worse. I had to draw a line in the sand with that assumption so basically went with the middle of the year. The calculator also allows for you to include assumptions as to how fast you expect your income and expenses to increase each year. Finally, you can enter whether your mortgage repayments will be weekly, fortnightly or monthly. You can then see a summary of the results at the top of the page and more detailed weekly balances below.

Also, if you weren’t using a revolving credit mortgage at the floating rate, chances are you may be using a fixed mortgage at a lower rate, so the calculator also shows the results for the savings you would make using an offset mortgage if you were fixed at a lower rate instead.

Have a play around with the different variables and see for yourself the difference changing spend and mortgage repayments from weekly to monthly may make. Then you can decide whether that is worth the hassle for you. You can also compare how well you may be off compared to other calculators on the website (offset and standard table mortgages).


impact of interest rates on mortgage calculator

With interest rates increasing from historic lows, many are wondering the impact that greater interest rate rises will have on the mortgage repayments. With this calculator you can put in your current mortgage information and compare that to a hypothetical, different interest rate. This will help how much you may need to tighten your belts if necessary.


maximum affordable mortgage calculator

With interest rates increasing, ever wondered how much scope you have before you can no longer afford the mortgage? This calculator will tell you the maximum interest rate you can have before you can no longer afford the mortgage at your current income and expenses.


Mortgage rate required when choosing between two or more terms


This calculator will let you know how much you need mortgage interest rates to increase or drop by to be better off choosing one mortgage term over another term. For more information on this calculator, have a read of our brief article here.


Mortgage and equity changes over time


Ever wondered how much of your mortgage payments go towards paying interest? Ānd at what point your repayments contribute more towards the principal than the mortgage?

This calculator will let you know how much of your payments are going towards principal pay down and how much towards bank interest over 5 year intervals up to 30 years.

At the same time, you will be able to see how much equity you have in the house relative to the bank loan. Otherwise known as loan to value. Again, the calculator shows the results in 5 year intervals up to 30 years.

Just enter your mortgage loan data in the purple cells. If you plan to make higher payments than the minimum then add those into row G purple cells.

Feel free to play around with different numbers to see the impact on the results.

There is some more information on this calculator in this brief blog article here.


Visual representation of how much of the mortgage has been paid off


This calculator is for all you visual people out there, who would rather deal in visuals than numbers. It is a picture of a crudely drawn house on Excel! You can see exactly how much of the mortgage has been paid off by seeing how much of the house has been coloured green. It is pretty motivating seeing more of the house filled with green as you progress.


Mortgage frequency calculator

There tends to be some confusion by people around savings made by paying the mortgage off fortnightly or weekly, rather than monthly. The common belief is that by paying off the mortgage weekly or monthly you make one extra mortgage payment per year, hence you will save many thousands of dollars over the term of the loan. However, this is not the case.

If you pay a mortgage weekly, you make 52 payments a year. If you pay fortnightly you make 26 payments a year at double the cost. Same annual payment. Whereas if you pay the mortgage monthly, people say you only make 12 payments per year and 12 is less than half of 26 fortnights. Hence you pay more on the mortgage if paying fortnightly due to paying more on the mortgage per year. However this is not the case. The banks calculate the monthly payment on a per day basis and because there are more than 4 weeks in most months, you pay more per mortgage payment per month than you do every second fortnight. Just wanted to dispel that commonly held belief!

Despite this, there are still some savings to be made by paying the mortgage off weekly rather than fortnightly or monthly, or fortnightly rather than monthly. Not because you are paying more (you aren’t, as described above). But because you are paying more of the mortgage off sooner than with higher but less regular payments.

The difference between paying the mortgage weekly or monthly isn’t huge over a significant time period, but check out the calculator yourself to see the difference changing the frequency of your mortgage repayments may make.


Break fee calculator


This calculator doesn’t calculate your break fee. Each bank calculates this slightly differently so you will need to contact them and ask them how much it would cost for you to break your fixed term mortgage.

Once you have your break fee information, this calculator will tell you whether or not breaking term will be worth it. Just enter your current home loan rate, your proposed home loan rate, the size of your loan, your break fee, and the months remaining on your loan. Then you will be told how much you will save (if anything) by breaking the mortgage term.

Just be cautious about calculating savings because even though you may save money by breaking term now, you may also be locking yourself in for another period of higher interest rates. Even though the rate may be lower than the rate you are paying now, it could be higher than future rates. You will need to decide if you are happy with the trade off for fixing now rather than later at potentially even lower rates. Your ‘savings’ for fixing now may not be savings at all if rates continue to drop and you are coming off term later than you would otherwise.


Mortgage to income ratio calculator

Banks are interested in how much the cost of owning a home takes up of your income. In other words, a measure of affordability. Why not get a jump start on the banks and get a measure of affordability first.

This calculator will show you how much of your in the hand income a mortgage will take up. It’s important to use in the hand income as that is the money you have available. Many other calculators use pre tax income but that is not practical. Why calculate income that isn’t yours to use? In addition, it will also show you how much all home ownership costs (not just the mortgage) will take up of your income. From there you can see if you are comfortable with that amount to live on, or if you would like to keep saving a bit more.

There is the option to enter up to 4 different loan terms in case you are getting out more than one loan term. The total across all loans will be calculated for you as a percentage of income.


Debt to income calculator (owner occupiers)


On the 1st of July 2024, banks now need to comply with new debt to income (DTI) restrictions set by the Reserve Bank.

DTI is a measure used by lenders to assess a borrower’s ability to meet their debt repayments. Basically, a measure to reduce a banks risk of taking on risky lending. A DTI ratio looks at the amount of debt someone has, relative to their before tax income. More debt or less income lends to a higher ratio which means it takes longer, and is more of a challenge, for a borrower to pay off a loan. Conversely, less debt and more income lends to a lower DTI ratio and is easier for a borrower to pay off a loan.

Some banks already use DTI measures, but the new rules have made it clear what rules the banks must follow. And these rules are that banks are not allowed to lend more than 6 times income for more than 20% of its total borrowers who are owner occupiers (not rental property investors).

Even if your DTI is higher than 6 (debt of more than 6 times gross income), there is still a small chance the bank can still lend to you. Up to 20% of its mortgage book is allowed to be to borrowers who have a DTI of greater than 6. However, that is dependent on the banks own lending criteria.

Now that most borrowers cannot borrow more than 6 times income, I thought it would be useful to add a new DTI calculator. In this calculator you can list all your sources of income and all your debts and have the totals added up for you. You will be informed:

  • How much house you can afford according to a DTI limit of 6.

  • What is the maximum size mortgage you are allowed.

  • How much less income you could have if the house you are looking at costs 10%, 20%, or 30% less than the maximum you can currently afford (6 times income).

  • How much more income you would need if the house you are looking at costs 10%, 20%, or 30% more than the maximum you can currently afford (6 times income).


Debt to income calculator (Investors)


The same restrictions apply to property investors with regards to the banks use of DTI measures. The only difference being that investors DTI ratio is 7, rather than 6. This means property investors borrowing money are allowed to have slightly more debt relative to income than a owner occupier.

This calculator is for those that hold investment property, where the DTI ratio is 7.


For personalised advice on the best way to take advantage of your housing asset(s) as part of your financial plan, then get in touch for a no obligations chat to see how we may be able to add value for you.

If you are interested in some of my musings on mortgages then check them out below:


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