Water Tank Size Calculator

The Water Tank Size Calculator finds the total water-holding capacity of a tank based on its shape and dimensions — useful for sizing storage tanks, irrigation systems, or any container where volume matters. Select your tank shape (rectangular, horizontal or vertical cylinder, or oval), enter the dimensions, and choose your dimension unit and output unit to get the Total Tank Volume. Optionally, enter a Fill Height to also see the Filled Volume and Remaining Capacity.

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Leave blank to calculate total capacity only

Results

Total Tank Volume

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Filled Volume

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Remaining Capacity

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Frequently Asked Questions

How do I calculate the volume of a water tank?

Tank volume depends on the shape. For rectangular tanks, multiply length × width × height. For cylindrical tanks, use π × radius² × height. Our calculator handles all common tank shapes automatically.

What's the difference between horizontal and vertical cylinder calculations?

Vertical cylinders are simpler - just multiply the circular base area by height. Horizontal cylinders require more complex calculations, especially for partial fill volumes, as the water forms a segment shape.

How accurate are these tank volume calculations?

Our calculations assume perfect geometric shapes. Real tanks may have wall thickness, fittings, or irregular shapes that slightly reduce actual capacity. These calculations provide reliable estimates for planning purposes.

Can I calculate partial fill volumes?

Yes, enter a fill height value to calculate how much water is currently in the tank and remaining capacity. This is useful for monitoring water levels and planning refills.

What units can I use for tank dimensions?

You can input dimensions in feet, inches, meters, or centimeters. Results can be displayed in US gallons, liters, cubic feet, or cubic meters to match your preferred measurement system.

Why are cylindrical tanks preferred over rectangular ones?

Cylindrical tanks distribute pressure more evenly, are stronger structurally, and use materials more efficiently. They're also easier to clean and have fewer corners where sediment can accumulate.

How do I size a tank for my water storage needs?

Consider your daily water usage, backup requirements, and local regulations. Typical homes need 1-2 days of storage capacity. Factor in fire protection requirements if applicable.