Useful next calculations
When to use this calculator
- Before comparing mortgage products, brokers or repayment types.
- When you want to test how a different deposit, rate or term changes the payment.
- When you need a quick estimate before using a formal illustration or agreement in principle.
- When you are stress-testing your budget against a higher rate.
A worked example
These are the example figures the calculator opens with.
| Input | Value |
|---|---|
| Annual Income (NZ$) | NZ$50,000 |
| Monthly Expenses (NZ$) | NZ$800 |
| Monthly Safety Buffer (NZ$) | NZ$500 |
| Interest Rate (%) | 5.5% |
For those figures the calculator returns:
- Payment-supported loan: NZ$466,817.30
- Mortgage payment budget: NZ$2,866.67
Method & assumptions
This planning calculator converts the monthly payment left after the spending and safety buffer you enter into a loan amount at the selected rate and term. It does not use a lender income multiple and does not replicate underwriting. The output is a payment-supported ceiling based solely on your assumptions, not an amount a lender has assessed as affordable.
Real lenders review income, debts, dependants, regular spending, credit history, loan-to-value and the effect of future rate rises under their own policies. Include all ongoing commitments and keep a realistic buffer rather than allocating every spare pound to a mortgage. Obtain a decision in principle from a regulated lender or mortgage adviser before relying on a borrowing figure.
Common mistakes
- Mixing up loan amount and property value, which distorts affordability and LTV.
- Using a headline rate but forgetting fees, insurance or repayment type.
- Testing only one term length instead of comparing payment and total cost together.
- Treating the result as a lender decision rather than a planning estimate.
What to do next
- Run a second scenario with a cautious assumption so you can see the downside clearly.
- Compare the result with the related calculators below before making a decision.
- Check current local rules, eligibility and provider terms before applying or committing money.
- Keep a record of the assumptions so you can update the estimate when a quote, bill or pay figure changes.