Tank Volume Calculator
Enter your tank shape and dimensions in inches to calculate total volume in cubic inches, cubic feet, gallons, and liters. Supports horizontal cylinders, vertical cylinders, and rectangular tanks.
Estimate only — not professional advice. Always verify results independently before purchasing materials or beginning work. Terms of Use
What is Tank Volume?
A tank volume calculator determines the total capacity of a storage tank based on its shape and dimensions. Knowing exact tank volume is essential for sizing water storage, fuel tanks, septic systems, chemical storage, rainwater harvesting, and agricultural applications. This calculator supports the three most common tank geometries: horizontal cylinders, vertical cylinders, and rectangular (box) tanks. Horizontal cylindrical tanks are the most common configuration for above-ground fuel storage, propane tanks, and industrial liquid storage. The tank lies on its side with the circular cross-section facing the ends. Volume is calculated as the area of the circular end (pi times radius squared) multiplied by the total length of the cylinder. For a 48-inch diameter tank that is 72 inches long, the end area is pi times 24 squared, or approximately 1,809.56 square inches, and the total volume is 1,809.56 times 72, or approximately 130,288 cubic inches. Vertical cylindrical tanks stand upright and are common for water storage towers, brewing vessels, and chemical processing. The calculation is identical to horizontal cylinders — pi times radius squared times height — but the orientation matters for fill-level calculations and structural support. Vertical tanks require a stronger base to support the full weight of the liquid. Rectangular tanks (also called box tanks or rectangular prisms) are used for water troughs, concrete forms, aquariums, and custom fabricated storage. Volume is simply width times length times height. While geometrically simpler, rectangular tanks are structurally less efficient than cylinders because flat walls must resist more hydrostatic pressure per unit area. All inputs use inches for maximum precision. The calculator converts cubic inches to cubic feet by dividing by 1,728 (12 cubed), cubic feet to US gallons by multiplying by 7.48052, and gallons to liters by multiplying by 3.78541. These conversions follow exact US standard liquid measurement definitions. One US gallon equals 231 cubic inches or 3.78541 liters. One cubic foot holds 7.48052 US gallons. These constants are essential for sizing pumps, calculating fill times, and determining weight (water weighs 8.34 pounds per gallon, or 62.4 pounds per cubic foot).
How to Calculate
- Select your tank shape: horizontal cylinder, vertical cylinder, or rectangular
- Enter the diameter (for cylinders) or width (for rectangular tanks) in inches
- Enter the length or depth of the tank in inches
- For rectangular tanks, enter the height in inches (ignored for cylinder shapes)
- Review the volume in cubic inches, cubic feet, gallons, and liters
- For partial fill calculations, multiply the total volume by the fill percentage
Formula
Horizontal or Vertical Cylinder: Volume (cu in) = pi x (Diameter / 2)^2 x Length Rectangular Tank: Volume (cu in) = Width x Length x Height Conversions: Volume (cu ft) = Volume (cu in) / 1,728 Volume (gallons) = Volume (cu ft) x 7.48052 Volume (liters) = Volume (gallons) x 3.78541 Where pi = 3.14159, 1,728 = 12^3 (cubic inches per cubic foot), 7.48052 = US gallons per cubic foot, and 3.78541 = liters per US gallon.
Example Calculation
A horizontal cylinder tank with a 48-inch diameter and 72-inch length: Radius = 48 / 2 = 24 inches Volume (cu in) = pi x 24^2 x 72 = 3.14159 x 576 x 72 = 130,288.13 cu in Volume (cu ft) = 130,288.13 / 1,728 = 75.40 cu ft Volume (gallons) = 75.40 x 7.48052 = 564.02 gallons Volume (liters) = 564.02 x 3.78541 = 2,135.04 liters
Frequently Asked Questions
How do I calculate the volume of a partially filled horizontal cylinder?
Partial fill in a horizontal cylinder requires a more complex formula involving the segment area of the circular cross-section. The formula is: Volume = Length x (R^2 x arccos((R - h) / R) - (R - h) x sqrt(2Rh - h^2)), where R is the radius and h is the liquid depth. This calculator provides total capacity; for partial fill, use a dedicated horizontal tank fill calculator.
How much does a full tank of water weigh?
Water weighs 8.34 pounds per US gallon, or 62.4 pounds per cubic foot. A 500-gallon tank holds 4,170 pounds of water. Always verify that the tank support structure and foundation can handle the full weight plus the weight of the tank itself. For reference, a 48-inch diameter by 72-inch long cylinder holds approximately 564 gallons, weighing about 4,704 pounds when full.
What is the difference between US gallons and Imperial gallons?
One US gallon equals 231 cubic inches or 3.78541 liters. One Imperial gallon equals 277.42 cubic inches or 4.54609 liters. Imperial gallons are about 20 percent larger than US gallons. This calculator uses US gallons. To convert the result to Imperial gallons, divide the US gallon figure by 1.20095.
Why are cylindrical tanks more common than rectangular ones?
Cylinders distribute internal pressure evenly across the curved wall, allowing thinner walls for the same pressure rating. A rectangular tank requires thicker walls and internal bracing because flat surfaces deflect under hydrostatic pressure. Cylinders also have less surface area per unit volume, reducing material costs and heat loss. Rectangular tanks are used when space constraints require a specific footprint.
How do I convert tank volume to fill time?
Divide the tank volume in gallons by the flow rate in gallons per minute (GPM). A 564-gallon tank filled at 10 GPM takes 564 / 10 = 56.4 minutes. Standard garden hoses deliver 3 to 5 GPM, residential well pumps deliver 5 to 15 GPM, and municipal hydrants can deliver 500 to 1,500 GPM.