What is a Cylindrical Water Tank?
A cylindrical water tank is a round water storage vessel manufactured from plastic (polyethylene), corrugated steel, or concrete designed to hold potable water, irrigation reserves, or fire protection water supplies. The cylindrical shape provides optimal strength against internal liquid pressure while minimizing wall material costs.
For drinking-water storage and tank management guidance, refer to the US EPA Drinking Water Storage Tank Assessment Study Protocol.
Cylindrical Water Tank Volume Formulas
Depending on how your cylindrical water tank is installed, the total storage volume and partial fill volume calculations use the following geometric formulas:
1. Vertical Cylindrical Water Tank Formula
For upright, vertical round tanks standing on a flat circular base:
Total Volume (V) = π × r² × h = π × (D / 2)² × h
Where:
- r = Radius of the circular base (half of internal diameter D)
- h = Vertical height of the tank
- π = Mathematical constant ≈ 3.14159265
Vertical Fill Volume: When partially filled to liquid depth d, Filled Volume = π × r² × d.
2. Horizontal Cylindrical Water Tank Formula
For horizontal cylindrical water storage tanks lying flat on their side:
Total Capacity (V) = π × r² × L = π × (D / 2)² × L
Where L is the total horizontal length of the cylinder body.
Horizontal Fill Volume (Partial Depth): Partial filling in horizontal cylinders follows circular segment area integration:
Segment Area (A) = r² × acos((r - d) / r) - (r - d) × √(2rd - d²)
Filled Volume = Segment Area (A) × Length (L)
Step-by-Step Example Calculation
Suppose you have a vertical cylindrical plastic water tank with an internal diameter of 6 feet and a height of 10 feet, filled with water up to a depth of 4 feet:
- Find the Radius: Radius
r = 6 ft / 2 = 3 ft. - Calculate Total Volume:
V_total = π × (3)² × 10 = 3.14159 × 9 × 10 = 282.74 cubic feet (ft³). - Calculate Filled Volume (at 4 ft depth):
V_filled = π × (3)² × 4 = 3.14159 × 9 × 4 = 113.10 cubic feet (ft³). - Convert to Litres and US Gallons:
Total Capacity in Litres = 282.74 × 28.31685 ≈ 8,006.47 Litres.Total Capacity in US Gallons = 282.74 × 7.48052 ≈ 2,115.06 US Gallons.
Standard Cylindrical Water Tank Capacity Reference Table
Below is a quick reference table showing approximate dimensions and volume capacities for standard vertical plastic (Poly) and steel cylindrical water tanks:
| Tank Capacity | Typical Diameter | Typical Height | Cubic Meters (m³) | Cubic Feet (ft³) |
|---|---|---|---|---|
| 500 Litres (132 gal) | 0.86 m (2.8 ft) | 0.95 m (3.1 ft) | 0.50 m³ | 17.66 ft³ |
| 1,000 Litres (264 gal) | 1.10 m (3.6 ft) | 1.15 m (3.8 ft) | 1.00 m³ | 35.31 ft³ |
| 2,500 Litres (660 gal) | 1.45 m (4.8 ft) | 1.60 m (5.2 ft) | 2.50 m³ | 88.29 ft³ |
| 5,000 Litres (1,320 gal) | 1.85 m (6.1 ft) | 1.95 m (6.4 ft) | 5.00 m³ | 176.57 ft³ |
| 10,000 Litres (2,640 gal) | 2.35 m (7.7 ft) | 2.40 m (7.9 ft) | 10.00 m³ | 353.15 ft³ |
| 20,000 Litres (5,280 gal) | 2.95 m (9.7 ft) | 3.05 m (10.0 ft) | 20.00 m³ | 706.29 ft³ |
Water Storage Weight & Load Considerations
When installing large cylindrical water tanks on roofs, elevated towers, or indoor slabs, calculating the total weight of stored water is vital for structural safety. Water has a high density:
- 1 Litre of fresh water = 1.0 Kilogram (2.205 lbs)
- 1 US Gallon of fresh water = 8.34 Pounds (3.785 kg)
- 1 Cubic Foot of fresh water = 62.43 Pounds (28.31 kg)
For instance, a 5,000 Litre cylindrical water tank weighs approximately 5,000 kg (5 Metric Tons / 11,023 lbs) when full. Ensure your foundation or structural concrete pad can safely support this dead load weight.
How to Use the Cylindrical Water Tank Calculator
Follow these quick steps to calculate your tank capacity instantly:
- Select Input Units: Choose feet, inches, meters, or centimeters for diameter and height/length.
- Enter Internal Diameter: Measure across the widest circular center of the tank.
- Enter Tank Height or Length: Enter vertical height for upright tanks or horizontal length for flat tanks.
- Enter Liquid Fill Depth (Optional): Input current water level to compute filled volume and percentage capacity.
- Click "Calculate Volume": Instantly view total capacity and filled volume in Litres, US Gallons, Imperial Gallons, Cubic Meters, and Cubic Feet.
For other tank shapes, explore our dedicated water tank volume calculator, vertical tank volume calculator, horizontal tank volume calculator, and plastic water tank calculator tools.