Master mortgage calculators to understand your borrowing power, repayments, and home loan affordability.
Calculate Your Borrowing PowerDifferent calculators serve different purposes in your home buying journey. Here's what each one does and when to use it.
Calculate your monthly mortgage payments based on loan amount, interest rate, and loan term.
Use when: You know how much you want to borrow and need to understand the repayment commitment.
Determines how much you can borrow based on your income, expenses, and deposit.
Use when: You want to know your maximum borrowing capacity before house hunting.
Assesses whether you can comfortably afford a property based on your income and expenses.
Use when: You want to ensure you're not overextending yourself financially.
Compares your current mortgage with potential refinancing options to calculate savings.
Use when: Considering switching lenders or restructuring your existing mortgage.
Shows how much interest and time you'll save by making additional mortgage payments.
Use when: Planning to make lump sum payments or increase regular repayments.
Repayment calculators are the most commonly used mortgage tool. Here's how to use them effectively.
Property price $750,000 minus $150,000 deposit
2-year fixed rate (check current rates)
Standard mortgage term in NZ
Even small rate changes significantly affect payments:
6.00%
$3,597/month
6.50%
$3,789/month
7.00%
$3,985/month
0.5% increase = $196 extra per month or $2,352 per year
Shorter terms mean higher payments but less total interest:
Borrowing calculators estimate your maximum loan amount, but banks use complex assessments. Here's what they consider.
Banks typically want your mortgage payment to be less than 30% of your gross (before-tax) income.
Based on 6.5% interest rate, 30-year term. Actual capacity depends on other factors.
Pro Tip: Cancel unused credit cards before applying for a mortgage. Banks assess your borrowing capacity based on credit limits, not balances. A $10,000 credit card limit might reduce your borrowing capacity by $40,000-$50,000.
Banks don't just assess whether you can afford repayments at today's interest rates. They stress test your ability to service the loan at higher rates.
Even if you're borrowing at 6.50%, banks assess affordability at approximately 8.50% (current rate + 2-3%).
Your Actual Rate
What you'll actually pay
6.50%
$3,789/month
Bank's Stress Test
You must afford this rate
8.50%
$4,612/month
Stress testing protects both you and the bank from interest rate increases. If you can only just afford repayments at current rates, you'd be in financial distress if rates rose by 2-3%.
Result: Your actual borrowing capacity is typically 15-20% less than simple calculator estimates suggest.
Pay off personal loans, car finance, and credit cards. Close unused credit card accounts. This can increase your borrowing capacity by $50,000-$100,000.
A larger deposit means borrowing less, making banks more comfortable lending to you. Going from 10% to 20% deposit also removes low equity premiums.
Different banks assess income and expenses differently. Brokers know which lenders will give you the highest borrowing capacity for your situation.
Connect with a brokerInclude bonuses, commissions, rental income, and side income. Banks can often use 80-100% of regular bonuses and 70-75% of rental income in their calculations.
30-year mortgages have lower monthly payments than 25-year mortgages, making you more affordable in the bank's eyes. You can always make extra repayments to pay it off faster.
If you're borderline, waiting 6-12 months to increase income, improve credit, or save more deposit can make a significant difference.
Interest rates change. Always calculate affordability at 1-2% higher than current rates to ensure you can handle rate rises.
Beyond mortgage payments, budget for rates ($2,000-$4,000/year), insurance ($800-$1,500/year), maintenance (1% of property value), and repairs.
Student loans, car finance, and credit card limits all reduce your borrowing capacity. Include everything for an accurate estimate.
You need 3-5% of purchase price for legal fees, valuations, LIM reports, building inspections, and moving costs. Don't use all your savings as a deposit.
Just because a bank will lend you $700,000 doesn't mean you should borrow that much. Leave financial breathing room for unexpected expenses and lifestyle.
They provide good estimates but aren't definitive. Banks use more complex calculations including stress testing, living expenses, and other debts. Treat calculator results as a guide, then get formal pre-approval for exact figures.
A good rule of thumb: your mortgage payment should be no more than 30% of your gross income, and ideally 25% or less. This leaves room for other expenses, savings, and lifestyle. If you're stretching to 40%+, you're likely overextending.
Use the current rate for the loan term you're considering (e.g., 2-year fixed). But also run calculations at 1-2% higher to stress test affordability. Your rate will change multiple times over 30 years.
No, most calculators only show principal and interest repayments. Budget an additional $250-$500/month for property rates, insurance, maintenance, and body corporate (if applicable).
If you can borrow $600,000, you can buy a property worth $750,000 with a 20% deposit. With a 10% deposit, you could buy a $667,000 property but would pay low equity premiums. Calculate backwards from your borrowing capacity to determine your price range.
30 years gives you lower required payments and more flexibility. You can always make extra repayments to pay it off in 25 years or less. The 30-year option also makes you more affordable in bank assessments, potentially increasing your borrowing capacity.
Get personalized calculations and pre-approval based on your actual financial situation
Calculate Your Borrowing PowerLast updated: March 24, 2026 | Rates and information verified with RBNZ