Rain Barrel Calculator
Estimate how much rainwater you can collect from your roof based on roof area and local rainfall.
Gallons Collected
748 gal
Gallons Collected vs Roof Catchment Area
Formule
## How Rain Collection Is Calculated One inch of rain on 1 square foot of roof produces about 0.623 gallons of water. ### Formula **Gallons = Roof Area (sq ft) x Rainfall (in) x 0.623 x Efficiency** Efficiency accounts for losses from gutters, splashing, and first-flush diverters.
Exemple Résolu
1,500 sq ft roof, 1 inch of rain, 80% collection efficiency.
- 01Raw collection = 1,500 x 1 x 0.623 = 934.5 gallons
- 02With 80% efficiency = 934.5 x 0.80 = 747.6 gallons
- 03Standard barrels = ceil(748 / 55) = 14 barrels
Questions Fréquentes
Is rainwater collection legal?
Laws vary by state/country. Most US states allow rainwater collection, some with permits. Check local regulations before installing a system.
What can I use collected rainwater for?
Primarily garden watering, lawn irrigation, and car washing. With proper filtration and treatment, it can be used for non-potable household use.
How much rain does an inch represent?
One inch of rain on a 1,000 sq ft roof yields about 623 gallons. A typical rainstorm of 0.5 inches on a 1,500 sq ft roof gives about 467 gallons.
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