Important Note : This calculator estimates internal tank capacity from ideal geometric shapes. It does not account for wall thickness, rounded ends, internal fittings, tilt, deformation, or manufacturer tolerance.

Use this Tank Volume Calculator to estimate total tank capacity, optional filled volume, and fill level for common tank shapes. It supports vertical cylinder tanks, horizontal cylinder tanks, and rectangular tanks, with dimension inputs in cm, m, inches, or feet and results in liters, cubic meters, US gallons, or cubic feet.

Reviewed by: AjaxCalculators Editorial Team
Last updated: April 25, 2026
Method source: Standard geometric volume formulas for cylinders, rectangular prisms, and partially filled horizontal cylindrical tanks
Editorial standards: AjaxCalculators Editorial Policy

What This Tank Volume Calculator Calculates

This calculator estimates:

• Total tank volume
• Filled volume when a filled height is entered
• Fill level percentage
• Capacity in liters
• Capacity in cubic meters
• Capacity in US gallons
• Capacity in cubic feet

The live tool supports three common tank shapes: vertical cylinder, horizontal cylinder, and rectangular tank. You can leave the filled height blank if you only want the total tank capacity.

How the Tank Volume Calculator Works

1) Vertical Cylinder Tank

For a vertical cylindrical tank, the total tank volume is calculated from the circular base area and the tank height.

Total volume = π × radius² × height

Since the calculator asks for diameter, the radius is:

radius = diameter ÷ 2

If a filled height is entered, the filled volume is calculated as a shorter cylinder using the same radius:

Filled volume = π × radius² × filled height

2) Horizontal Cylinder Tank

For a horizontal cylindrical tank, the total volume is still based on the cylinder formula:

Total volume = π × radius² × tank length

However, the filled volume is more complex because the liquid forms a circular segment inside the round tank. The calculator estimates the filled cross-section area first, then multiplies that area by the tank length.

Filled volume = circular segment area × tank length

This is why the filled height is especially important for horizontal tanks. A tank that is half full by height is half full by volume, but below or above the halfway point, the relationship between height and volume is curved rather than linear.

3) Rectangular Tank

For a rectangular tank, the volume is calculated by multiplying length, width, and height.

Total volume = length × width × height

If a filled height is entered, the filled volume uses the same base length and width but replaces the full tank height with the filled height:

Filled volume = length × width × filled height

4) Fill Level

When a filled height is entered, the calculator can also estimate the percentage of the tank that is filled.

Fill level = filled volume ÷ total volume × 100

This percentage is based on volume, not just the height reading.

Supported Tank Shapes

• Vertical cylinder: useful for upright water tanks, drums, barrels, and storage vessels.
• Horizontal cylinder: useful for horizontal fuel tanks, liquid storage tanks, and round tanks lying on their side.
• Rectangular tank: useful for box-shaped water tanks, aquariums, storage containers, and rectangular reservoirs.

Supported Units

The calculator lets you enter tank dimensions using:

• centimeters
• meters
• inches
• feet

You can view the calculated result in:

• liters
• cubic meters
• US gallons
• cubic feet

Assumptions and Important Notes

• This calculator assumes the tank has a regular geometric shape.
• For cylindrical tanks, the diameter is treated as the internal tank diameter.
• For rectangular tanks, length, width, and height are treated as internal dimensions.
• The filled height should not be greater than the full tank height or diameter.
• Horizontal cylinder filled volume is calculated using circular-segment geometry.
• The result is an estimate and may differ from real tank capacity if the tank has rounded ends, thick walls, internal fittings, dents, slope, or manufacturing tolerances.
• The calculator does not account for unusable volume, overflow clearance, sediment space, or safety reserve volume.

Worked Example: Vertical Cylinder Tank

Suppose you have a vertical cylindrical tank with a diameter of 2 meters and a height of 3 meters.

Step 1: Find the radius
Radius = 2 ÷ 2 = 1 meter

Step 2: Calculate total volume
Total volume = π × 1² × 3
Total volume ≈ 9.425 cubic meters

Step 3: Convert cubic meters to liters
1 cubic meter = 1,000 liters
9.425 × 1,000 ≈ 9,425 liters

So, the tank can hold approximately 9,425 liters when completely full.

Worked Example: Rectangular Tank with Filled Height

Suppose you have a rectangular tank that is 2 meters long, 1 meter wide, and 1.5 meters high. If the filled height is 1 meter, the filled volume is:

Total volume
2 × 1 × 1.5 = 3 cubic meters

Filled volume
2 × 1 × 1 = 2 cubic meters

Fill level
2 ÷ 3 × 100 = 66.67%

This means the tank is holding about 2,000 liters, or roughly 66.67% of its total capacity.

How to Use This Tank Volume Calculator

1. Select the tank shape: vertical cylinder, horizontal cylinder, or rectangular tank.
2. Select the dimension unit you want to use.
3. Select the result unit you want to display.
4. Enter the required tank dimensions.
5. Enter the filled height if you want to calculate filled volume.
6. Leave filled height blank if you only want total tank volume.
7. Click Calculate to view total volume, filled volume, and fill level.

How to Interpret the Result

Total volume is the estimated full internal capacity of the tank.

Filled volume is the estimated amount of liquid or material inside the tank based on the filled height you entered.

Fill level shows the filled volume as a percentage of total capacity.

For rectangular and vertical cylindrical tanks, filled height changes volume in a mostly direct way. For horizontal cylindrical tanks, the volume changes along a curve because the filled cross-section is a circular segment.

Practical Uses of a Tank Volume Calculator

• estimate water tank capacity
• calculate fuel tank volume
• estimate aquarium or rectangular container volume
• convert tank capacity between liters, gallons, cubic meters, and cubic feet
• check how much liquid is stored at a certain fill height
• plan storage capacity for construction, agriculture, irrigation, or household use

Common Mistakes to Avoid

• Do not mix outside dimensions with inside dimensions if the tank wall is thick.
• Do not enter radius when the calculator asks for diameter.
• Do not enter filled height greater than the tank height or diameter.
• For horizontal cylinder tanks, do not assume 25% of height always means 25% of volume.
• Use the same unit system consistently for all dimensions.

References

1. AjaxCalculators live Tank Volume Calculator
2. CalculatorSoup: Tank volume formulas for vertical, horizontal, and rectangular tanks
3. Math Is Fun: Volume of a partially filled horizontal cylinder
4. Cuemath: Rectangular prism volume formula

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Disclaimer: This calculator is for educational, planning, and estimation use only. Real tank capacity can vary because of wall thickness, rounded ends, fittings, slope, deformation, and manufacturer specifications. For engineering, fuel storage, pressure vessels, chemical storage, or regulated systems, confirm capacity using the tank manufacturer’s official data or a qualified professional.