Gutter Calculator
Size gutter capacity and downpipe count from catchment area and rainfall intensity.
Estimate only — not a substitute for a licensed tradesperson, a certified engineer, or sign-off from your local building surveyor. Verify against current standards and site conditions before ordering materials or starting work.
Result
- Peak flow rate
- 375L/min
- Downpipes required
- 3
Indicative sizing only. Final gutter/downpipe sizing must follow AS/NZS 3500.3 and local rainfall intensity data.
What this is based on
Governed by AS/NZS 3500.3 (Stormwater drainage). Gutter and downpipe sizing comes from that standard's tables, which are a licensed compilation and are deliberately NOT encoded or reproduced here - this calculator works from values you supply (catchment area, design rainfall intensity, downpipe capacity). Design rainfall intensity for your location comes from AS/NZS 3500.3 / Bureau of Meteorology data, not from this calculator. Confirm sizing against the standard or with your plumber.
We cite the clause and link to the publisher so you can read the source yourself. We do not reproduce the text or tables of the NCC or of any Australian Standard.