💧 Cistern Capacity Calculator Water Storage

Calculate water volume in rectangular, cylindrical, and oval cisterns | US Gallons | Imperial Gallons | Liters | Cubic Feet

🏺 What is a Cistern?

A cistern is a waterproof receptacle for holding water, typically used for rainwater harvesting, fire suppression, or backup water storage. This calculator helps determine the capacity of rectangular, cylindrical, and oval cisterns with support for feet+inches input, multiple unit outputs (US Gallons, Imperial Gallons, Liters, Cubic Feet), fill/empty time, and rainwater catchment estimation.

Rectangular Cistern Dimensions (Feet + Inches)

ft in
ft in
ft in

⏱️ Fill / Empty Time Calculator

☔ Rainwater Catchment Calculator

Cistern Capacity & Analysis Results

US Gallons
0
gal (US)
Imperial Gallons
0
gal (UK)
Liters
0
L
Cubic Feet
0
ft³

📋 Fill / Empty Time Estimates

⏱️ Time to Fill (at 10 GPM):0 hours
⏱️ Time to Fill (at 600 GPH):0 hours
💧 Time to Empty (at 10 GPM):0 hours

☔ Rainwater Catchment Potential

🌧️ Annual Catchment Potential:0 US gallons
🏠 Number of Cisterns Filled Per Year:0
💧 Gallons per 1 inch of rain:0 US gallons
📏 Roof Area Equivalent for this Cistern:0 sq ft

📏 Dimensions & Volume Breakdown

Shape:Rectangular
Dimensions (converted to feet):—
Volume (cubic feet):0 ft³
Cubic Meters:0 m³
Weight of Water:0 lbs / 0 kg

🏠 Usage Recommendations

Household (4 people) - Days of Water:0 days
Garden Irrigation - Coverage:0 sq ft
Fire Suppression Rating:—

Cistern Capacity Calculator – Complete Water Management Tool

This comprehensive cistern capacity calculator helps you determine water storage volume in multiple units: US Gallons, Imperial Gallons, Liters, and Cubic Feet. The feet+inches input makes it easy to enter measurements exactly as you measure them on site.

The rainwater catchment calculator estimates how much water you can collect from your roof annually, helping you size your cistern correctly. The fill/empty time calculator helps you understand pump and pipe requirements for your water system.

Frequently Asked Questions

How do I convert feet and inches to decimal feet?
Decimal feet = Feet + (Inches ÷ 12). For example, 5 feet 6 inches = 5 + (6÷12) = 5.5 feet. This calculator does this conversion automatically for you.
What is the difference between US Gallons and Imperial Gallons?
A US Gallon is 3.785 liters, while an Imperial Gallon (UK) is 4.546 liters. Imperial gallons are about 20% larger. This calculator provides both outputs.
How do you calculate rainwater catchment?
Multiply Roof Area (sq ft) × Annual Rainfall (inches) × 0.623 × Efficiency. Each inch of rain on 1,000 sq ft yields ~623 gallons at 100% efficiency. Typical collection efficiency is 85% due to losses.
What flow rate should I use for fill time?
For municipal fill: 5-15 GPM typical. For well pumps: 5-10 GPM. For rainwater gravity feed: 2-5 GPM. Use your actual pump or pipe capacity for accurate estimates.