Rates & sources
Monthly payment via the standard annuity formula. Rates change daily — always confirm with your lender.
Source: Bank of England — Effective interest rates — figures refreshed at the start of each tax year.
When to use this calculator
- Before comparing lenders, brokers, or repayment options.
- When you want to test how a different deposit, rate, or term changes affordability.
- When you need a quick estimate before using a formal quote or agreement in principle.
- When you are stress-testing your budget against a potential rate rise to see the impact on monthly payments.
- When you want to understand the full cost of borrowing — not just the monthly figure — before you commit.
A realistic Australia planning example
Use these sample inputs as a quick scenario test, then change one variable at a time to compare outcomes.
Loan Amount (A$)
A$560,000
Property Value
A$700,000
Interest Rate (%)
5%
Term (Years)
25 years
After entering these figures, review monthly payment, total interest and ltv together rather than in isolation — each metric tells a different part of the story. Then rerun the tool with one input adjusted to see which variable has the biggest effect on all three outputs before you settle on a plan.
How to read your results
Monthly Payment
Use this to check whether the scenario fits comfortably within your regular budget. If it looks tight, rerun the tool with a longer term or larger deposit to find the boundary of affordability.
Total Interest
This shows the long-run cost of borrowing beyond the original principal, which is especially useful when comparing terms or weighing up overpayment options. A shorter term usually cuts this figure significantly even if the monthly payment rises.
LTV
Loan-to-value helps you compare product eligibility and understand how much lender risk you are carrying at this deposit level. Crossing key LTV thresholds — typically 90%, 85%, or 75% — can unlock materially better interest rates.
Method & assumptionsAuthoritative sources
This calculator works on a standard capital and interest repayment basis, spreading your loan across the chosen term so that each monthly payment reduces the outstanding balance while also covering interest. The calculation uses compound interest applied monthly, which is how virtually all UK residential mortgage lenders price their products. The result shows an illustrative monthly payment based on the rate and term you enter — it does not account for mortgage fees added to the loan, payment holidays, or rate changes at the end of a fixed period. Real-world repayments may differ slightly depending on how your lender calculates daily interest. Always request a full Key Facts Illustration (KFI) or European Standardised Information Sheet (ESIS) from any lender before committing.
Common mistakes
- !Mixing up loan amount and property value, which can distort affordability and LTV.
- !Using a headline rate but forgetting fees, insurance, taxes, or repayment type.
- !Testing only one term length instead of comparing the payment and total cost together.
- !Forgetting that a repayment mortgage and an interest-only mortgage produce very different monthly figures and total costs.
- !Not accounting for the impact of a rate revert after an introductory fixed period ends, which can sharply increase payments.
What to do next
- Run a second scenario with a higher rate or shorter term so you can see the downside clearly.
- Compare the result with an affordability or overpayment calculator before applying.
- Use the related guides below to understand trade-offs before you request live quotes.
- Note down the monthly payment and total interest for your two or three strongest scenarios so you have a clear comparison ready when you speak to a broker.
- Check whether making a modest overpayment each month would reduce total interest significantly — run the overpayment calculator next to find out.
Frequently asked
Use arrow keys to navigate items, Enter or Space to expand/collapse.
End-of-article next steps
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