How it works
Harvested litres = rainfall mm × roof catchment m² × efficiency fraction; one mm over one m² equals one litre.
Input definitions
- CSV: period,rainfall mm
- Plain text; maximum 200,000 characters.
- Roof collection area (m²)
- Enter the value in the labeled unit.
- Collection efficiency (%)
- Enter the value in the labeled unit.
A worked example
- CSV: period,rainfall mm
- period,rainfall January,50 February,40
- Roof collection area (m²)
- 100
- Collection efficiency (%)
- 80
Assumptions & limits
Your entered rainfall and efficiency, no local weather feed. No potable-water safety, tank structural or plumbing compliance assessment.
Sources & review
Maintained by AnsRio. Methods and examples use automated checks; this does not imply independent professional certification.
Method updated 2026-10-17. Content checked against the stated method and examples. Our verification approach.
Common questions
Does estimated rainwater collection equal usable stored water?
No. Storage capacity, overflow, first-flush diversion, demand and rainfall timing affect how much can actually be used. This worksheet estimates collected volume from rainfall totals.
How does Rainwater collection worksheet work?
Harvested litres = rainfall mm × roof catchment m² × efficiency fraction; one mm over one m² equals one litre.
What are the limits of Rainwater collection worksheet?
Your entered rainfall and efficiency, no local weather feed. No potable-water safety, tank structural or plumbing compliance assessment.
How do I keep the full worksheet?
Run the tool and choose Download file. The on-page table is a preview and may show only the first 20 rows; the downloaded file contains the full result. CSV downloads escape spreadsheet formula prefixes. Inputs and files are processed on your device.