Rainfall Calculator — Calculate Rainfall Volume & Water Collection

Rainfall Calculator

Calculate rainfall volume, water collection potential, and runoff estimates for any area. Perfect for gardeners, farmers, rainwater harvesting, and irrigation planning.

Step 1: Area Specifications

25 mm
85%

Understanding Rainfall Collection

Collection efficiency accounts for losses due to evaporation, runoff, and surface absorption. Roof collection typically has 85-95% efficiency, while ground collection may be 50-75% efficient.

Step 2: Calculation Parameters

Rainfall Volume Formula

Volume (liters) = Area (m²) × Rainfall (mm) × Collection Efficiency. 1 mm of rain on 1 m² = 1 liter of water. This calculator helps estimate water harvesting potential for sustainable water management.

Rainfall Calculation Results

Summary
Monthly Comparison
Breakdown

Collected Rainfall Volume

2,125 L
From 25 mm rainfall on 100 m²
Area Size
100 m²
Rainfall Amount
25 mm
Collection Efficiency
85%
Total Rainfall Volume
2,500 L

Monthly Rainfall Collection Comparison

Month Avg. Rainfall Collected Volume Equivalent Showers

Rainfall Collection Breakdown

Rainfall Volume Formula

Volume (liters) = Area (m²) × Rainfall (mm) × Collection Efficiency (%)

To calculate collected rainwater: Multiply area in square meters by rainfall in millimeters, then multiply by collection efficiency percentage (as a decimal). 1 mm of rain on 1 m² equals 1 liter of water.

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