Mortgage Stress Test Calculator NZ
This calculator checks whether you could still afford your mortgage repayments if interest rates rose, the same stress test lenders apply before approving a loan. You enter your loan amount, the loan term in years, your current interest rate, and a higher test rate you want to check yourself against. The calculator works out your principal and interest repayment at both rates over the remaining term and returns your current repayment, your stressed repayment at the test rate, the extra amount you would pay each month, and what that adds up to over a year. Because banks typically test loans against a rate a few percentage points above the one you are actually paying, running the same check yourself shows whether you have a genuine buffer or are borrowing right to your limit. It is useful whether you are a buyer working out how much you can safely borrow, or an existing homeowner wanting to see how much your repayments could rise at the next refix. Try raising the test rate to see how sensitive your budget really is to another round of rate rises. Repayments are calculated on a standard table (principal and interest) basis, and the results are an indicative estimate only, not financial advice, so check your own numbers with your lender before making borrowing decisions.
Repayments are calculated on a table (principal and interest) basis over the remaining term. A test rate a few percentage points above your current rate is a sensible resilience check. Make sure your budget could absorb the extra before borrowing to your limit. Estimate only, not financial advice.
How it works
The calculator works out the principal and interest repayment on your loan at both your current rate and a higher test rate, over the term you enter. The difference is what your repayments would rise by if rates climbed to the test level. Seeing this in advance shows whether you have a comfortable buffer or are stretched, which is exactly what a lender checks before approving a loan.
Worked example
A $600,000 loan over 30 years at 6.5% costs about $3,792 a month. At an 8.5% test rate, the repayment rises to around $4,614, an extra $822 a month or close to $9,900 a year. If your budget could not absorb that, it is a sign to borrow less or build a bigger buffer.
Related calculators
- Mortgage Repayment Calculator: standard repayments.
- Borrowing Capacity Calculator: how much you can borrow.
- Mortgage Interest Rate Comparison Calculator: compare rates.
- House Affordability Calculator: what you can afford.