Mortgage calculators
Free mortgage calculators, all downloadable Excel spreadsheets — yours to keep, change and re-run whenever your rate or your plans change. Enter your details in the purple cells and the results work themselves out. No email required.
Most New Zealand mortgages are table loans: equal repayments over the life of the loan, where each payment covers both interest and principal. Early on, most of what you pay is interest, and it takes years before the balance starts moving properly. Nearly every calculator below is built on that structure — with separate ones for offset and revolving credit loans, which work differently.
If you're not sure where to start, Mortgage calculator with extra payments is the one most people want. It shows what the loan costs, and what paying a bit more does to that. If you're coming off a fixed term, start with how long to fix. If you're wondering how much you can borrow, start with debt to income.
PAYING IT OFF SOONER
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. If you have more than one mortgage or your mortgage is split over various loan terms, then check out the multiple mortgages calculator.
Mortgage calculator with optional extra payments
How much extra do I need to pay?
This calculator lets you know how much extra you will need to pay on the mortgage to have it paid off by your desired timeframe. For example, if you would like to pay off a mortgage in 15 years, rather than the current 25 years, this calculator will let you know how much more than the minimum repayments you will need to add per month to meet your payoff target.
The calculator will also show how much mortgage interest you would save by making extra mortgage repayments.
Extra payments required on mortgage calculator
How many years to pay off the mortgage?
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.
How many years to pay off the mortgage calculator
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.
Mortgage payoff, coloured in
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.
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 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.
Pay off the mortgage or invest calculator
IF YOUR RATE CHANGES
Compare your repayments at a different rate
Coming off a fixed term, or wondering what a rate move would do to your payments? Enter your current mortgage and a hypothetical rate — higher or lower — and see the difference.
Impact of higher (or lower) interest rates on your mortgage calculator
What happens when my rate changes?
It can be quite unnerving to see mortgage rates increasing as your loan is about to come off term. Conversely it can be quite exciting to see rates coming down as you are about to come off term.
This calculator can let you see how changes in interest rate affect how much your new monthly payments will be so there are no nasty surprises. It may even help you decide what new loan term to choose based on what you can afford.
You just need to enter your loan size, duration, and current interest rate.
From there, you will see the results for a wide range of interest rates (including interest free), without having to enter any changes to interest rates yourself.
Change in mortgage interest rates calculator
The maximum rate you could afford
How far could rates rise before the mortgage stops being affordable on your current income and expenses? Useful to know before you're anywhere near it.
Maximum mortgage interest rate you can afford calculator
WHERE YOU STAND
What will my loan balance be at the end of the term?
This information can be found in the comprehensive calculators above, however it can get lost in the detail. This calculator makes this information front and center.
Great if you are interested in knowing what your loan balance will be at the end of the loan term.
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.
Mortgage to income ratio calculator
Mortgage and equity changes over time
Ever wondered how much of your mortgage payments go towards paying interest? And 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.
Mortgage and equity changes over time calculator
CHOOSING A BANK OR LOAN
Which bank’s mortgage offer is best?
It can be hard to compare apples to oranges when comparing one banks mortgage offering to another. Some have higher set up fees, others have higher cashback offerings, and then you have the different interest rates on offer.
This easy to use calculator lets you see which banks offering would you see you best off financially over the timeframe of the loan you are contemplating. You can compare up to three bank offerings.
There is of course more to mortgages than which will save the most money, such as loan structures, ease of banking, customer service, quality of app and so. But let’s face it, value for money is top of the list for most.
Multiple mortgages calculator
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.
BIGGER DECISIONS
These six each have enough to them to warrant their own page — the calculators, the rules, and what the numbers don't tell you.
How long should I fix my mortgage for?
Choosing your next fixed term is one of the few money decisions that arrives with a deadline attached, and most people make it in a hurry with whatever the bank puts in front of them.
Five calculators, now on their own page:
Historical NZ mortgage rates, monthly since 2004
Which fixing strategy has performed best (with 10,000 simulations)
The rate required to break even between two terms
Delay to fix — does waiting on floating pay?
Blended interest rate, if you split the loan
→ How long should I fix my mortgage for?
Debt to income calculator (owner occupiers and investors)
Since 1 July 2024, banks have had to work within Reserve Bank limits on how much they can lend relative to your income — 6 times gross income for owner-occupiers, 7 for investors. That's now often the thing that decides what you can borrow, rather than your deposit or what you can afford to repay.
→ Work out your DTI and your maximum mortgage
Offset mortgage calculator
An offset mortgage links your savings to your home loan and only charges interest on the difference. Work out what it would save you, what rate you're effectively paying, and whether it beats simply fixing at a lower rate.
Revolving credit mortgage calculator
A revolving credit mortgage works like a large overdraft against your house — income in, expenses out, interest charged daily on the balance. Work out what it would save you, how much to put on it, and whether it beats fixing at a lower rate.
→ Revolving credit mortgage calculator
Break fee calculator
Your bank is the only one who can tell you what breaking your fixed term will cost — but they won't tell you whether it's worth it. Bring their figure, your current rate and the rate you'd move to, and find out whether you'd actually be better off.
→ Mortgage break fee calculator
debt recycling calculator
Debt recycling turns non-deductible mortgage interest into deductible investment interest, without borrowing any more than you already have. Two calculators — one for how much you can recycle and the tax it saves, one comparing recycling against not recycling against simply paying down the mortgage.
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 I may be able to add value for you.
If you are interested in some of my musings on mortgages then check them out below: