Rainwater Event Volume Budget calculator.
Separate rainfall volume, supplied capture losses and available tank space.
Your inputs
Use measurements from your plan and properties from your chosen product. Any prefilled values are illustrative.
A clear estimate starts here.
Enter your dimensions and product details to see the quantity and purchase breakdown.
Formula and assumptions
How this calculation works.
Uses horizontal catchment area for the supplied rainfall depth. Stored volume is bounded by the entered usable capacity; hydraulic capacity and drinking-water suitability are excluded.
A worked example
Illustrative inputs only. Product properties and design dimensions are not recommendations for your project.
- Supplied catchment plan area
- 100 m²
- Entered event rainfall depth
- 10 mm
- Supplied captured share
- 80 %
- Specified event diversion volume
- 0.1 m³
- Supplied usable storage capacity
- 1 m³
- Current stored volume
- 0.5 m³
Event volume retained in available storage: 0.5 m³
Rainfall and capture share are user inputs, not weather predictions. This arithmetic budget does not size gutters, pipes or overflows, assess water quality or promise collection performance.
Before you purchase
Use dimensions from your plan and properties from your chosen product. Any design spacing, section or fixing pattern must already be specified.
Uses horizontal catchment area for the supplied rainfall depth. Stored volume is bounded by the entered usable capacity; hydraulic capacity and drinking-water suitability are excluded.
Dimensions, quantities, prices, timing and product properties are supplied by you. This tool does not select construction specifications or assess structural, electrical or hydraulic suitability.
Method: dimensional arithmetic and user-supplied specifications. Software checks: 2026-10-04. Calculation and review policy.