How we calculate
How we work out each limit, the choices we made where banks do not publish theirs, our assumptions, and every engine test with its result.
Advertised rates as at 10 November 2026. Test rates confirmed 13 July 2026. Rules checked 10 November 2026.
Methods, and why we chose them
The answer
We work out three limits and take the lowest: serviceability, the debt-to-income limit and the deposit (LVR) limit. The result says which one binds and why. Banks decide; this is an estimate.
Serviceability
Money left each month = take-home pay + the counted share of rent − living costs − other debt repayments − any buffer. The loan it supports is the present value of an annuity: loan = surplus × (1 − (1 + r)^−n) / r, with r the test rate divided by 12 and n = 360 months. The formula comes from the shared engine our repayment site uses.
Test rates
Each bank’s published test rate, confirmed in July 2026 by interest.co.nz and MPA. We default to the average of the five banks (6.94%) so we favour no bank, and show every bank alphabetically. The 30-year test term comes from secondary sources only.
Living costs: our assumption
Banks compare your living costs with internal benchmarks they do not publish. We use the higher of your figure and our own floor: $1,600 a month for the first adult, $800 for each other adult and $500 for each dependent child. These are our assumptions, not bank figures. You can turn the floor off.
DTI limit
Gross income (including all rent) × 6 for owner-occupiers or × 7 for investors, less existing debts, including the full limits of credit cards and overdrafts. Exactly 6 is within the limit; above 6 is high.
Deposit (LVR) limit
Loan = deposit × LVR / (1 − LVR): 80% for owner-occupiers, 70% for investors, 95% for a First Home Loan, or the share you choose for a low-deposit loan or a new build. Exactly 80% is within the rule; above 80% is high.
Exemptions
First Home Loans are exempt from the LVR limits and, per secondary sources, DTI; new builds from both. We show an exempt limit as exempt. We could not confirm the current wording on rbnz.govt.nz.
Rent
We count 75% of rent for serviceability (two sources say 70% to 80%), and all of it as income for DTI, as Kiwibank describes.
Price range
Loan plus deposit at each bank’s test rate, from the toughest to the easiest. Repayments are at the average advertised 1-year rate across the five banks, the same dated table our repayment site uses, rounded up to the cent.
What we leave out
Tax: you enter take-home pay. Credit card limits: counted for DTI, but not as a monthly cost, because banks do not publish the share they use. Buying costs come out of the deposit you enter.
Where the rates come from
Bank test rates come from interest.co.nz, confirmed 13 July 2026. Advertised rates come from the same weekly table as our repayment site, dated 10 November 2026. A rate never appears on this site without its date.
Engine tests
Every borrowing case in our research file (HL-01 to HL-14) runs before each build, with our engine checks, and the build stops on any failure. On 10 November 2026: 58 passed, 0 failed.
| Check | Basis | Result | Detail | Source |
|---|---|---|---|---|
| HL-01 DTI ratio | sourced | Pass | expected 6.25, got 6.25 | Source |
| HL-01 owner-occupier high DTI | sourced | Pass | expected true | Source |
| HL-02 DTI 600000/100000 | computed from sourced rule | Pass | expected 6, got 6 | Source |
| HL-02 high DTI flag at 6 (owner-occupier) | computed from sourced rule | Pass | expected false, got false | Source |
| HL-02 DTI 601000/100000 | computed from sourced rule | Pass | expected 6.01, got 6.01 | Source |
| HL-02 high DTI flag at 6.01 (owner-occupier) | computed from sourced rule | Pass | expected true, got true | Source |
| HL-03 investor DTI | computed from sourced rule | Pass | expected 7, got 7 | Source |
| HL-03 investor at 7 is not high | computed from sourced rule | Pass | expected false | Source |
| HL-04 max total debt at DTI 6 | computed from sourced rule | Pass | expected 720000, got 720000 | Source |
| HL-04 max new home loan after the card limit | computed from sourced rule | Pass | expected 710000, got 710000 | Source |
| HL-05 LVR 640000/800000 | computed from sourced rule | Pass | expected 0.8, got 0.8 | Source |
| HL-05 high LVR flag at 0.8 (owner-occupier) | computed from sourced rule | Pass | expected false, got false | Source |
| HL-05 LVR 640080/800000 | computed from sourced rule | Pass | expected 0.8001, got 0.8001 | Source |
| HL-05 high LVR flag at 0.8001 (owner-occupier) | computed from sourced rule | Pass | expected true, got true | Source |
| HL-06 investor LVR | computed from sourced rule | Pass | expected 0.7, got 0.7 | Source |
| HL-06 investor at 70% is not high | computed from sourced rule | Pass | expected false | Source |
| HL-06 investor deposit for standard lending | computed from sourced rule | Pass | expected 270000, got 270000 | Source |
| HL-07 deposit firstHomeLoan5pct | computed from sourced rules | Pass | expected 35000, got 35000 | Source |
| HL-07 deposit standard20pct | computed from sourced rules | Pass | expected 140000, got 140000 | Source |
| HL-07 deposit investor30pct | computed from sourced rules | Pass | expected 210000, got 210000 | Source |
| HL-08 First Home Loan premium1_2pct | computed from sourced rule | Pass | expected 6840, got 6840 | Source |
| HL-08 First Home Loan kiwibankFee1_0pct | computed from sourced rule | Pass | expected 5700, got 5700 | Source |
| HL-08 First Home Loan oldRate0_5pct | computed from sourced rule | Pass | expected 2850, got 2850 | Source |
| HL-09 First Home Loan eligibility: 1 buyer(s), 0 dependant(s), $95000 | computed from sourced rule | Pass | expected true, got true | Source |
| HL-09 First Home Loan eligibility: 1 buyer(s), 0 dependant(s), $95001 | computed from sourced rule | Pass | expected false, got false | Source |
| HL-09 First Home Loan eligibility: 1 buyer(s), 1 dependant(s), $150000 | computed from sourced rule | Pass | expected true, got true | Source |
| HL-09 First Home Loan eligibility: 2 buyer(s), 0 dependant(s), $150000 | computed from sourced rule | Pass | expected true, got true | Source |
| HL-09 First Home Loan eligibility: 2 buyer(s), 0 dependant(s), $150001 | computed from sourced rule | Pass | expected false, got false | Source |
| HL-10 KiwiSaver withdrawal from $25000 | computed from sourced rule | Pass | expected 24000, got 24000 | Source |
| HL-10 KiwiSaver withdrawal from $800 | computed from sourced rule | Pass | expected 0, got 0 | Source |
| HL-10 KiwiSaver withdrawal from $30000 ($5000 from Australia) | computed from sourced rule | Pass | expected 24000, got 24000 | Source |
| HL-11 loan $3000 a month supports at 6.85% | computed | Pass | expected 457834.08, got 457834.0814 | Source |
| HL-12 loan $3000 a month supports at 7.1% | computed | Pass | expected 446407.34, got 446407.3408 | Source |
| HL-13 low equity premium rate (UNVERIFIED rates) | computed from single-source rates | Pass | expected 0.0075, got 0.0075 | Source |
| HL-13 low equity premium a year | computed from single-source rates | Pass | expected 4500, got 4500 | Source |
| HL-14 gross rent a year | computed (default is a choice, see research s 3.4) | Pass | expected 33800, got 33800 | Source |
| HL-14 rent counted at 75% | computed (default is a choice, see research s 3.4) | Pass | expected 25350, got 25350 | Source |
| engine: DTI thresholds and speed limits match the rules file | engine | Pass | 6 and 7, 20% each | Source |
| engine: LVR thresholds and speed limits match the rules file | engine | Pass | 80% and 70%, 25% and 10% | Source |
| engine: bank test rates match the rules file | engine | Pass | ANZ 6.85%, ASB 6.85%, BNZ 7.1%, Kiwibank 6.95%, Westpac 6.95% | Source |
| engine: First Home Loan deposit, caps and premiums match the rules file | engine | Pass | 5%, $95,000 / $150,000, 1.2% and 1.00% | Source |
| engine: KiwiSaver, low equity premiums, rent share and cost ranges match the rules file | engine | Pass | 3 years and $1,000; Canstar bands; 75% (70 to 80%); cost ranges | |
| engine: principalForPayment and tablePayment round trip to the cent | engine | Pass | loan 485506.99 back to 3210.5500 a month | |
| engine: at a 0% rate the surplus supports surplus x months | engine | Pass | got 1800000 | |
| engine: serviceability binds when it is the lowest limit, and the loan equals it | engine | Pass | loan 710745.16; DTI 755000; LVR 800000.0000000002 | |
| engine: LVR binds with a small deposit (loan = deposit x 4 at 80%) | engine | Pass | loan 400000.0000000001, LVR 0.8 | |
| engine: DTI binds with high take-home and a big deposit (6 x income less debts) | engine | Pass | loan 575000, DTI after 6 | |
| engine: First Home Loan path lends to 95% and is DTI exempt | engine | Pass | LVR limit 759999.9999999993 | |
| engine: investors use 7 x income and a 30% deposit (no First Home Loan) | engine | Pass | DTI limit 885000, LVR limit 699999.9999999999 | |
| engine: our living-cost floor applies when entered costs are lower (our assumption, labelled) | engine | Pass | used 2400 | |
| engine: no surplus means no serviceability, and serviceability binds | engine | Pass | surplus -600 | |
| engine: banks listed alphabetically, and a higher test rate never lends more | engine | Pass | ANZ 717273, ASB 717273, BNZ 699372, Kiwibank 710026, Westpac 710026 | |
| engine: average of the five test rates is 6.94% | engine | Pass | got 6.94 | |
| engine: borrowing exactly the DTI limit leaves DTI at 6, which is not high | engine | Pass | limit 600000 | |
| engine: the LVR limit loan sits exactly at 80%, not above it; a dollar more is high | engine | Pass | loan 640000.0000000001 | |
| engine: low equity bands split at 80%, 85%, 90% and 95% | engine | Pass | bands -1, 0, 1, 2, 3 | |
| engine: KiwiSaver first-home withdrawal needs 3 years of membership | engine | Pass | 2.9 years no, 3 years yes | |
| engine: debts reduce the DTI limit dollar for dollar, including card limits | engine | Pass | never below zero |