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If you have any comments, suggestions, or issues please reach out using the form. I consider all ideas! 🙂
Or reach out to firstname.lastname@example.org
Latest feedback from users
Best loan repayment calculator I ever used, thank you!
Did I mention this is EVERYTHING I've been looking for, for YEARS. Sending you virtual beers. Bloody excellent!! This is actually life changing in terms of forecasting and making decisions with funds going into loan vs offset
Amazing. So easy to use
Awesome work mate! Hands down the best calc I've seen. Super easy to use and gives me all the answers I want. Love it!
This is amazing, makes its so much easier to understand for someone like me
Very easy to use and all the highlights of important information is just lined up there. Definitely love this calculator. Thank you!
Absolutely incredible, just the other day I was searching for a calculator that could figure out when I would fully offset my loan
OMG thank you - this is just what we were looking for !!
The best mortgage calculator I have used. So easy to use
Thank you so much! Such an excellent calculator!
This is a great calculator, thank you so much for providing it. I have been manually trying to do this myself but your obvious skills and expertise mean I have a more accurate idea of my loan and the impact of payments etc over the years.
A fantastic calculator, thanks for your help and well done 👍
Fantastic work ! Best I have used
Great job, really useful and easy to use!
Frequently asked questions
It simulates the entire loan term by processing every calendar date one by one. For a 30 year loan, over 10,950 days are calculated in less than a second. This is the only accurate method of calculating interest, and the first Australian home loan calculator to do so.
This is the only calculator that:
- Calculates interest daily.
- Always charges interest monthly.
- Shows true interest savings of weekly/fortnightly repayments.
- Generates a complete transaction schedule.
- Allows extra repayments to be made at any interval.
- Supports withdrawals.
- Supports offset account transactions.
- Tracks amount paid in advance.
- Supports existing loans by allowing the actual repayment amount to be entered, and duration in months.
- Accounts for leap years in interest calculations.
- Can account for proper rounding methods of interest and charges.
- Shows interest calculations per day.
- Supports various interest calculation methods.
- Supports various repayment calculation methods for fortnightly/weekly repayments.
The calculator is still in Beta and being tested. There might be some things I've overlooked.
I've verified accuracy of interest calculations with two major Australian banks, so I have some confidence in the results. I'll be collecting sample data from other lenders for further testing.
I'm not sure I'll ever be able to calculate to 100% precision, but I plan to get as close as possible. There are many nuances between Australian lenders that make this difficult.
Support offset facilities that offer a discounted rate, rather than a full offset of the loan balance.
Interest rate fluctuation
Visualise the effects of interest rate fluctuations for new loans. (Delayed - harder than I thought)
Sometimes your loan may be repaid sooner than your loan term, even if you haven't made extra repayments.
Some possible reasons:
- You're making fortnightly or weekly repayments, so you're saving interest in reducing your loan balance more frequently.
- Some lenders calculate weekly or fortnightly repayments by splitting the monthly repayments by 2 fortnights, or 4 weeks. You end up paying roughly an extra 4 weeks of repayments per year.
- You entered a really high interest rate (over 15%), which can amplify inaccuracies between repayment calculations and interest.
After your last repayment, there may be a closing payment added to balance the loan. This is expected.
The formula lenders use to calculate your minimum repayments is not completely accurate. It doesn't account for the odd numbers of days per month or extra days in leap years (when using the "Actual/365" interest calculation method).
Is your chart trending upwards? 📈 It's probably because you're overriding the "Minimum repayment" with an amount too low to cover interest charges.
This could also happen when combining an extremely high interest rate with the "Actual/365" interest calculation method. This effectively charges an additional day of interest every leap year, which the repayment formula was not built to factor in.
Surprisingly most Australian lenders use the "Actual/365" interest method, but some use "Actual/Actual" which evenly distributes interest across every day, including leap years.
I saw a thread on Reddit where people were confused and couldn't agree whether weekly repayments saved interest compared to monthly repayments. Some quoted results of online loan calculators that showed minimal savings, and in some cases zero.
I looked into it and realised the calculators were all wrong. Their formulas are flawed because they charge interest at the same time as repayments. This provides inaccurate results for weekly or fortnightly repayments which are only charged interest monthly. I also discovered other errors in their algorithms which caused further inaccuracies...
For many people home loans are the biggest financial decisions and burdens of their lives. I thought it was silly that in this massive Australian home loan market, no lender provides an accurate calculator. I wanted to make a tool that provided more transparency where lenders haven't, and educate people about home loans in the process.
- I designed a temporal algorithm using
- The calculation occurs client-side, which I opted for rather than an external API which would affect performance.
- The algorithm is heavy, so it's offloaded to a separate thread using a web worker to clear up the main thread.
- The transaction schedule uses
react-virtualized, which renders table rows on the fly as you scroll. This enables thousands of transactions to be displayed without affecting performance or memory.
- Styled components for CSS.
- Website: Server-side rendered / statically generated with Next.js.
- Handmade components which I plan to release as an open-source design system. The amount of external dependencies used is minimal.
This calculator is provided as a free tool. I do not profit from this or offer financial products. The calculator is still actively under development and requires further testing. You should treat results as an estimate only and they should not be used as a substitute for professional advice.
While I’ve tried to create a preset based on the most common loan products in Australia, the results may not reflect your actual loan circumstances. If you find this calculator isn’t suitable for you or providing incorrect results, please submit feedback and I'll seek to improve it.
The repayment calculation may differ from your actual repayments depending on your lender’s policy. For example, your lender may round up to the nearest dollar. You can override the repayment amount using the “Amount” field. For existing loans, enter your repayment amount manually as the calculator is unable to figure this out (repayments are based on your initial loan amount). Australian lenders use various methods for calculating weekly or fortnightly repayments because they're converted from a monthly figure. You can modify the method used in the calculations using the repayment “Calculation method” field.
Interest is calculated daily on the current loan balance to 5 decimal places. At the end of the monthly period the total is then rounded to 2 decimal places before being charged. The calculator always charges interest monthly on the same day each month, except when the first interest charge falls on the 29th, 30th, or 31st. Following months with less days will instead charge interest on the last day of the month (this behaviour also applies to monthly repayments). The calculator assumes the interest rate will remain the same throughout the entire loan. In reality, a variable interest rate can fluctuate and affect repayments and interest (I’m working on an interest rate fluctuation feature). The default interest calculation method is “Actual/365” but it can be modified. Check with your lender to see what applies to you.
Your loan may include fees which are not included in these calculations. You can add them under “Extra transactions”. If for whatever reason the loan will not be repaid within the specified loan term, the final repayment will include the outstanding balance of the loan. This can happen because repayment calculations do not factor in all aspects of a loan's schedule. For example, you may be able to recreate this scenario by using an extremely high interest rate with the “Actual/365” interest calculation method. Every leap year it charges an additional day of interest. The higher the interest rate, the more these small inaccuracies are amplified.
100% of the offset account balance is offset against the loan balance when calculating interest. Your lender may offer only a partial offset. I am planning on adding support for partial offset accounts. If the offset account balance is greater than the outstanding loan, the calculator assumes the loan continues for remainder of the term while not accruing interest. Depending on your lender, they may automatically close the loan in this event.