Kitchen
Kitchen Rangehood Size Calculator
Recommends extractor fan size and extraction rate for a hob
Updated 26 June 2026 · Live
What this tool does
Recommends extractor fan size and extraction rate for a hob.
Formula Used
Spotted something off?
Calculations or display — let us know.
People also use
How the kitchen extractor / hood size calculator works
Recommends extractor fan size and extraction rate for a hob. The calculator takes your dimensions and supplier rates, applies a standard Australian trade formula, and returns a quantity with an indicative cost. Every figure is an estimate — site conditions always move the final number.
Typical Australian kitchen wastage
Cabinets and benchtops are cut to size — wastage is in the offcuts (typically 10% by m²) and any mismeasure that needs re-ordering. Our defaults reflect common Australian trade allowances, and can be adjusted upwards for non-standard geometry or downwards where experience supports a lower figure.
What this tool does not do
It does not replace a professional quote, factor regional pricing, assess structural adequacy, or confirm National Construction Code (NCC) compliance. Those remain the responsibility of a suitably qualified designer, surveyor, or your building surveyor.
On-site considerations for kitchen extractor / hood size
Extractor ventilation and electrical circuits must meet Approved Documents F and P. A new cooker hood above 400 m³/h typically needs dedicated ducting, not recirculation.
the National Construction Code (NCC) and compliance
Kitchen electrical work (new circuits, additional sockets beyond a same-circuit extension) is notifiable under AS/NZS 3000. Use a licensed trade electrician to self-certify. When in doubt, a pre-application enquiry to the local council can give early clarity, which tends to be less costly than retrospective correction.
Before you order
Order sanitaryware, benchtops, and cabinets on the same lead time so site sequence does not stall. Benchtops typically sit at 4–6 weeks from template to delivery. Cross-checking the calculator’s output against a supplier quote helps catch differences in pricing assumptions — ask for exact product specifications (grade, finish, batch number) and confirm delivery timescales against your programme.
Adjusting the defaults
Every input in this calculator is editable. Enter your own dimensions, supplier prices, and wastage allowance — the output recalculates instantly. If the defaults feel off for your region or project type, your own numbers always override them.
Using this kitchen extractor / hood size calculator alongside other BuildMetricLab tools
This calculator works best as part of a planning workflow. Pair the quantity with our project contingency, labour-hours, and material-cost calculators to build a complete estimate before you pick up the phone to a supplier. All BuildMetricLab tools run entirely in your browser — no sign-up, no data sent anywhere, and every formula is shown on-page so you can audit the maths.
Sources & methodology
Recommends extractor fan size and extraction rate for a hob. Every result is calculated from the values you enter, and all inputs are editable.
Frequently asked questions
Are kitchen extractor / hood size calculator results accurate enough to order materials?
Use them as a starting estimate only. Verifying the final quantity with your supplier or contractor before ordering is good practice — site conditions, wastage and cut-offs all affect the true figure.
What wastage percentage should I use?
The calculator defaults to the typical Australian trade allowance for kitchen. Increase it for complex cuts, awkward shapes, or first-time DIY. The default wastage allowance reflects common trade practice; values lower than the default may underestimate offcuts.
Does this replace professional advice?
No. This tool is a planning estimator. For works that affect structure, the National Construction Code (NCC), boundary or dividing-fence, gas, electrics, drainage to a sewer, or similar, consult a suitably qualified professional.
Can I change the unit prices?
Yes — every price field is editable. Plug in your supplier's quote to get a total that matches your project.
Related tools
Calculators from other categories that planners often reach for next.