ENGINEERING TOOL

Rainwater Harvesting Calculator

Estimate collected rainwater from rainfall, horizontal roof area and collection efficiency.

Rainwater Harvesting Calculator

FREE ONLINE TOOL

Calculation preview

Roof area: 100 m²
Collected water: 4,000 L

Schematic · not to scale

Formula and assumptions

V (L) = R (mm) × A (m²) × η (%)/100

Rainfall must cover the period of interest. Efficiency includes runoff and filter losses. This yield estimate does not size storage or guarantee water quality.

STEP BY STEP

How to use rainwater harvesting calculator

Check the input units and assumptions.
Review the result and example.

IN PRACTICE

Example

50 mm × 100 m² × 80% = 4000 L = 4 m³.

GOOD TO KNOW

How is this result calculated?

Collected volume (L) = rainfall (mm) × horizontal roof area (m²) × efficiency/100. Rainfall must cover the period of interest. Efficiency includes runoff and filter losses. This yield estimate does not size storage or guarantee water quality.

Rainwater Harvesting Calculator

Rainwater Harvesting Calculator

Formula and assumptions

How to use rainwater harvesting calculator

Example

How is this result calculated?

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