Ultimate Rainwater Harvesting & Collection Calculator

ByMarry Issac Posted on

The Ultimate Rainwater Harvesting & Collection Calculator helps you quickly estimate how much rainwater you can collect from your roof and how large a tank or rain barrel system you need. By entering your roof size, rainfall, runoff coefficient, and storage preferences, this tool instantly calculates roof runoff volume, harvestable rainwater, recommended barrel size, and ideal tank capacity. It also provides monthly and annual water collection estimates, making it perfect for homeowners, gardeners, farmers, and anyone planning a rooftop rainwater harvesting system. Easy to use and fully accurate, this calculator helps you design an efficient and cost-effective water collection setup for your home or garden.

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Ultimate Rainwater Harvesting & Collection Calculator

Calculate roof runoff, harvestable rainwater, tank sizing, and storage capacity for your rainwater collection system.

🏠 Roof Runoff Calculator

Calculate how much rainwater you can collect from your roof based on size, rainfall, and surface type.

Roof Area 1,200 sq ft
Water Collected Per Rainfall Event
572 gallons
2,165 liters
Based on 1 inch of rainfall
💡 Tip: 1 inch of rain on 1 sq ft of roof = 0.623 gallons

🌧️ Rainwater Harvesting Calculator

Estimate your monthly and annual harvestable rainwater based on local rainfall data.

Roof Area: 1,200 sq ft
Efficiency: 85%
Month Rainfall (in) Harvestable (gal)
0
0
0
0
0
0
0
0
0
0
0
0
Total Annual Rainfall
45.7 inches
Annual Harvestable Water
26,152 gallons
98,991 liters

🛢️ Rain Barrel & Tank Size Calculator

Determine how many rain barrels you need or the ideal tank size for your rainwater collection.

Water Collected (per event): 572 gallons
🛢️
Rain Barrels Needed
12
for single rainfall event
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Recommended Tank Size

Storage Analysis

Your Desired Storage: 500 gallons
Water per Event: 572 gallons
Status: Shortage: 72 gallons overflow

🛢️ Common Tank Sizes

  • Rain Barrels: 35-65 gallons - Small gardens
  • IBC Totes: 275-330 gallons - Medium collection
  • Cisterns: 500-2,500 gallons - Whole-home use
  • Large Tanks: 5,000+ gallons - Agricultural/commercial

📊 Storage Capacity Calculator

Calculate how much storage you need based on your daily water usage and desired backup days.

Quick Usage Presets

Required Storage Capacity
350 gallons
1,325 liters
For 7 days of usage at 50 gallons/day

📈 Storage Comparison

Annual Harvest Available: 26,152 gallons
Annual Usage (estimated): 18,250 gallons
Annual Balance: +7,902 gallons surplus

📊 Collection Summary

🏠
Roof Area
1,200 sq ft
🌧️
Per Event
572 gal
📅
Annual Harvest
26,152 gal
🛢️
Rec. Storage
350 gal

Ultimate Rainwater Harvesting Calculator • Version 1.0 • WordPress Shortcode: [rainwater_harvesting_calculator]

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