ALL HOME LOAN CALCULATORS MADE SIMPLE: THE SMART BORROWER’S GUIDE

If you’re buying a home, refinancing, or investing in property, home loan calculators are the fastest way to understand your numbers before you commit. In seconds, they can show how much you can borrow, what your repayments might be, and how much interest you could save—without speaking to a lender.

Why Home Loan Calculators Matter (and Why Millions Use Them)

Home loan calculators help borrowers estimate costs, compare options, and make better decisions before applying for (or changing) a mortgage. They use inputs like income, expenses, loan amount, interest rates (fixed or variable), and loan terms (principal and interest or interest-only) to deliver instant estimates—so you can plan with confidence.

All Home Loan Calculators Made Simple (Complete Breakdown)

Repayment Calculator (Principal & Interest vs Interest-Only)

What does a mortgage repayment calculator do?
A home loan repayment calculator estimates your regular repayments—weekly, fortnightly, or monthly—based on the loan amount, interest rate, loan term, and repayment type.

Inputs

• Loan amount
• Interest rate
• Loan term (e.g. 30 years)
• Repayment type (P&I or interest-only)
•  

Shows

• Repayment amount
• Total interest payable
• Total loan cost over time

Best for

• Understanding affordability
•  
• Comparing mortgage rates
•  
• Seeing the difference between interest-only and principal & interest loans

Ratebuster’s Home Loan repayment calculator here.

Borrowing Power Calculator (How Much Can I Borrow?)

How much can I borrow using a borrowing power calculator?
A borrowing power calculator estimates the maximum loan amount a lender may approve, based on your income, expenses, and existing debts.

Inputs

• Income (single or joint)
• Living expenses
• Existing debts (credit cards, car loans, HECS/HELP)
• Interest rate buffer

Shows

• Estimated borrowing limit

Best for

• First-home buyers
•  
• Early planning before inspections
•  
• Understanding lender serviceability rules

Stamp Duty Calculator

What is a stamp duty calculator?
A stamp duty calculator estimates government stamp duty payable when buying property in Australia.

Inputs

• Purchase price
• State or territory
• Buyer type (first-home buyer, owner-occupier, investor)
•  

Shows

• Stamp duty payable
• Concessions or exemptions (if eligible)
•  

Best for

• Budgeting upfront costs
• Avoiding settlement shortfalls
•  

Click here for our stamp duty calculator

Loan Comparison Calculator

How does a loan comparison calculator work?
A loan comparison calculator compares two or more home loans side-by-side to show which option costs less over time.

Inputs

• Loan amount
• Interest rate
• Fees
• Loan term

Shows

• Total interest over the life of the loan
• Potential savings between options

Best for

• Choosing between lenders
• Balancing rate vs fees
• Long-term cost comparison

Refinance Calculator

Is refinancing worth it? Use a refinance calculator.
A refinance calculator estimates how much you could save by switching home loans.

Inputs

• Current loan balance
• Current interest rate
• New interest rate
• Refinance costs
• Cashback offers (if applicable)

Shows

• Monthly repayment savings
• Lifetime interest savings
• Break-even point

Best for

• Existing homeowners
• Evaluating cashback refinance deals
• Reducing repayments or shortening the loan term

Westpac Refinance calculator here.

Extra Repayments Calculator

How much faster can I pay off my home loan?
An extra repayments calculator shows how additional repayments reduce interest and loan duration.

Inputs

• Loan amount
• Interest rate
• Extra repayment amount

Shows

• Years shaved off the loan
• Interest saved

Best for

• Paying off your mortgage faster
• Using bonuses or salary increases effectively

Offset Account Calculator

What does an offset account calculator show?
An offset account calculator estimates interest savings from money held in an offset account linked to your home loan.

Inputs

• Loan balance
• Offset balance
• Interest rate

Shows

• Interest saved
• Reduced loan term

Best for

• Homeowners with savings
• Tax-effective interest reduction (especially for owner-occupiers)

Ratebuster’s mortgage offset calculator can easily be accessed from the knowledge hub or here

Redraw vs Offset Calculator

Redraw vs offset: which is better?
A redraw vs offset calculator compares interest savings, access, and flexibility between the two options.

Shows

• Interest saved under each option
• Access differences
• Potential tax implications (for investors)

Best for

• Strategic loan structuring
• Investors and forward planners

LMI (Lenders Mortgage Insurance) Calculator

What is an LMI calculator?
An LMI calculator estimates lenders mortgage insurance when borrowing above 80% of a property’s value.

Inputs

• Property value
• Loan amount

Shows

• Approximate LMI premium

Best for

• Low-deposit buyers
• Assessing 5–10% deposit strategies

Rent vs Buy Calculator

Should I rent or buy?
A rent vs buy calculator compares the long-term financial outcomes of renting versus owning.

Inputs

• Rent amount
• Property price
• Interest rate
• Capital growth assumptions

Shows

• Estimated net wealth difference over time

Best for

• Lifestyle vs financial decisions
• Long-term planning

First Home Buyer Calculator

What help can first-home buyers get?
A first home buyer calculator bundles grants, stamp duty concessions, and loan costs.

Shows

• Total upfront cost
• Government assistance
• Required savings

Best for

• First-home buyers navigating incentives

Loan Term Reduction Calculator

What happens if I shorten my loan term?
A loan term reduction calculator shows how changing your loan term affects repayments and total interest.

Best for

• Switching from 30 to 25 or 20 years
• Balancing cash flow vs interest savings

Investment Property Calculator

How does an investment property calculator help?
An investment property calculator estimates cash flow, tax impact, and yield.

Inputs

• Rental income
• Loan interest
• Expenses
• Tax rate
•  

Shows

• Positively or negatively geared outcome
•  

Best for

• Property investors
• Portfolio planning

Split Loan Calculator

Should I split my home loan?
A split loan calculator models a loan split between fixed and variable rates.

Best for

• Managing interest rate risk
• Balancing certainty and flexibility

Quick Summary: Home Loan Calculators at a Glance

Finance Calculators Explained

Budget Calculator

What is a budget calculator?
A budget calculator helps you understand your monthly cash flow by comparing your income with your regular expenses.

What it does

• Calculates how much money comes in versus goes out
• Shows whether you’re spending more than you earn
• Highlights surplus or shortfall each month

You enter

• Income (salary, bonuses, other income)
• Fixed expenses (rent, mortgage, utilities, insurance)
• Variable expenses (food, transport, entertainment)

What it shows

• Monthly surplus or deficit
• Where your money is going

Best for

• Understanding your financial position
• Preparing for a home loan or refinance
• Identifying areas to cut spending

Access all Ratebuster calculators. Here is the Ratebuster budget calculator.

Savings Goal Calculator

What is a savings goal calculator?
A savings goal calculator shows how long it will take to reach a savings target based on regular contributions.

It does

• Estimates the time needed to reach your savings goal
• Shows how contribution amounts affect timelines

What you enter

• Target savings amount
• Current savings balance
• Regular savings amount (weekly or monthly)
• Estimated interest rate (if applicable)

What it shows

• Time required to reach your goal
• Total contributions versus interest earned

Best for

• Saving for a home deposit
• Planning emergency funds
• Setting realistic financial milestones (Moneysmart)

Compound Interest Calculator

What is compound interest?
A compound interest calculator shows how savings grow when interest is earned on both your original balance and previously earned interest.

It does

• Calculates long-term savings growth
• Demonstrates the power of regular deposits

What you enter

• Starting balance
• Regular deposit amount
• Interest rate
• Investment timeframe

It shows

• Final balance over time
• Total interest earned

Best for

• Long-term saving strategies
• Understanding why starting early matters
• Comparing saving versus investing outcomes

Income Tax Calculator

What does an income tax calculator do?
An income tax calculator estimates how much tax you’ll pay based on your annual income.

It does

• Calculates estimated tax payable
• Shows take-home (after-tax) income

What you enter

• Annual income
• Employment type (if applicable)

it shows

• Estimated tax payable
• Net income after tax

Best for

• Budgeting more accurately
• Estimating true borrowing capacity
• Understanding take-home pay before applying for a mortgage

For official tax rates and thresholds, see the Australian Taxation Office

What Can I Afford to Borrow? (Borrowing Power Calculator)

How much can I afford to borrow?
A borrowing power calculator estimates the maximum home loan amount you may be eligible for based on your income and expenses.

It does

• Estimates borrowing capacity for a mortgage
• Factors in living expenses and existing debts

What you enter

• Income (single or joint)
• Monthly living expenses
• Existing loans and credit limits
• Interest rate buffer

it shows

• Estimated maximum loan amount

Best for

• First-home buyers
• Early property planning
• Setting realistic price ranges
•  

Common Features of Home Loan Calculators (What to Look For)

Principal and Interest Breakdowns

Good calculators show how each repayment is split between principal and interest, helping you understand how your balance reduces over time.

Amortisation Schedules Explained

Amortisation schedules visualise your repayment journey, showing how interest decreases and principal increases as the loan matures.

Extra Repayment Options and Benefits

Even small extra repayments can significantly cut years and interest. Quality calculators demonstrate this clearly.

Lump Sum Payments and Savings

Simulating lump sum payments shows how bonuses or windfalls can accelerate repayment and reduce total interest. (Commonwealth Bank):

Key Terms Explained (Plain English)

• Principal & Interest (P&I): Repayments reduce the loan balance and pay interest.
•  
• Interest-Only (IO): Repayments cover interest only for a set period.
•  
• Fixed vs Variable: Fixed rates stay the same for a term; variable rates can change.
•  
• LVR (Loan-to-Value Ratio): Loan amount as a percentage of property value; affects rates and LMI.
•  

FAQs About Home Loan Calculators

Are home loan calculators accurate?
Home loan calculators provide estimates, not approvals. Accuracy depends on the quality of inputs and lender assessment rules.

Do banks use the same borrowing power calculators?
No. Each lender applies different serviceability buffers, expense benchmarks, and policies.

Which home loan calculator should I use first?
Most buyers start with a borrowing power calculator, then use a repayment calculator once a price range is clear.

Why do mortgage calculator results differ?
Results differ due to interest rate assumptions, expense inputs, buffers, and fees included or excluded.

Where to Compare Home Loans and Go Deeper

Trusted comparison platforms like RateBuster help borrowers compare rates, features, and cashback offers—but calculators are the first step to understanding your numbers.

Ready to Take the Next Step?

Now that you’ve seen the meaning/use of all home loan calculators, put them to work.

Explore the RateBuster’s Calculators page under knowledge hub or simply click here. Make smart decisions.

We offer free home loan comparison in one easy step. click here