Printable Rainwater Harvest Calculator
This sheet is for anyone tracking rainwater harvesting from a roof. It includes a rainwater estimate table with columns for Month, Rain (in), Roof (sq ft), Efficiency, and Gallons collected. The sample rows use April, May, and June with a 1200 square foot roof and 0.8 efficiency.
Free printable · PDF
- 2 pages
- US Letter — choose “Fit to page” for A4
- PDF, 51 KB
Free for personal, family and classroom use.
Enter your roof footprint in square feet, monthly rainfall in inches, and collection efficiency. Use 0.8 for 80 percent efficiency, or adjust it to match your setup. Fill in each month to compare how much water your roof can collect across the year.
Good for
- Estimate monthly rainwater harvest
- Compare roof collection across seasons
- Plan tank storage needs
Tip: Print it and keep one sheet per roof or location for cleaner monthly comparisons.
4 files · XLSX, PDF, DOCX
Get every sheet: Rainfall Record Book
This sheet plus 3 more in one download, with the editable Excel and Word files. Excel annual rainfall workbook with monthly totals and normals comparison, printable daily rain gauge logs, a rainwater harvesting calculator and a garden watering log.
$5.00 USD, one-time 4 files · about $1.25 each
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Printable Annual Rainfall Summary Workbook
Printable Daily Rain Gauge Log
Printable Garden Watering Log