Vent Sizing Calculator
Screen a vent size from fixture units using the simplified lookup currently embedded in this calculator. Its table has not been verified as a complete sizing method for every supported region; do not use it as plumbing approval.
How the estimate works
The current lookup returns 40 mm through 10 fixture units, 50 mm above 10 through 30, 65 mm above 30 through 100, and 100 mm above 100; a length over 50 m can raise a 40 mm result to 50 mm.
Metric worked example
Inputs: 10 fixture units; vent length 12 m
Working: 10 units is at the top of the first lookup band; 12 m is below the calculator's 50 m length trigger
Result: Calculator output: 40 mm (screening only; verify local sizing method)
Units and regional checks
Vent sizing tables and permitted configurations differ across NZ, AU, US, UK and Canada. The application's simplified lookup is not region-specific; verify the current local source before installation.
Frequently asked questions
Can I use one vent sizing rule in every region?
No. This calculator currently applies one simplified lookup and is not verified as a complete method across its supported regions. Confirm the governing local requirements.
Open the interactive calculator