Maximum borrowing
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How Interest Rates Affect Mortgage Affordability
Explore how changes in mortgage interest rates affect monthly repayments and overall affordability.
Inputs
Results
Maximum house price
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Maximum monthly payment
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Income multiple
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How interest rate changes are modelled
Borrowing capacity in this model is income-driven, while interest rate changes the monthly repayment required to service that borrowing.
Use this page to stress-test payment affordability across different mortgage rate assumptions.
Example using current inputs
$80,000.00 × 4.5 = $360,000.00
$360,000.00 + $30,000.00 = $390,000.00
Why interest rate context matters
In this model, income multiple drives borrowing, while interest rate primarily changes monthly repayment pressure.
Use this page to compare repayment sensitivity across rate assumptions so you can budget with an appropriate safety margin.
What drives the estimate
- Total annual household income
- Income multiple used on this page (4.5x)
- Deposit amount
- Selected interest rate for repayment estimation
Assumptions and limitations
This tool provides deterministic estimates for planning and comparison. Real lender outcomes may differ because of underwriting rules and risk policy.
- Income-multiple model is simplified and not lender-specific
- Monthly payment assumes a 25-year repayment structure
- Credit profile, existing debts, fees, taxes, and insurance are not modelled
- Regional lending policy and stress testing can change final approval
Frequently asked questions
How much mortgage can I afford based on my income?
Using this page's current inputs, $80,000.00 at 4.5x may support around $360,000.00.
Does interest rate affect how much I can borrow?
In this income-multiple model, interest rate changes monthly repayment cost but does not directly change maximum borrowing.
What is the difference between borrowing amount and property price?
Borrowing amount is the loan. Property price is borrowing plus deposit. Example: $360,000.00 + $30,000.00 = $390,000.00.
Does changing deposit affect borrowing amount?
Deposit does not change the income-based borrowing output in this model; it changes total property budget by adding to borrowing.
Why is this estimate different from lender offers?
Lenders may apply stress tests, credit checks, debt commitments, and policy rules that are not included in this simplified income-multiple estimate.
Can I use this calculator outside the US?
Yes. The model is country-agnostic for estimation, but lender criteria and affordability rules vary by market.
How is monthly mortgage payment estimated?
Monthly payment is estimated using a standard repayment amortisation formula over 25 years at your selected interest rate.
Can I change assumptions and compare scenarios?
Yes. Update income, second income, deposit, and interest rate to instantly compare affordability scenarios on the same page.