Tank Volume Calculator

Estimate total and filled capacity for rectangular, vertical cylindrical or horizontal cylindrical tanks

Rectangular: A = length, B = width, C = height. Cylinders: A = diameter and B = height/length. For a horizontal cylinder, fill level is liquid depth as a percentage of diameter.

Your result will appear here.

About the Tank Volume Calculator

Tank capacity starts with the vessel’s internal geometry, not its outside shell dimensions. This calculator converts usable internal dimensions into theoretical liquid capacity for storage planning, water systems and process vessels.

Geometric capacity is not always usable capacity. Headspace, fittings, internal equipment, sloped bottoms and minimum operating levels can reduce the amount of liquid that can actually be stored.

How to Use the Tank Volume Calculator

  1. Choose the tank shape that matches the vessel, such as rectangular, cylindrical or another supported form.
  2. Enter internal dimensions when you want liquid capacity rather than outside shell volume.
  3. Calculate the geometric volume and convert it to litres, gallons or another useful unit.
  4. Apply operating headspace or unusable-volume allowances separately when the real tank cannot be filled to the theoretical maximum.

How the Calculation Works

A rectangular tank uses V = length × width × height. A vertical cylinder uses V = πr²h, while horizontal or other supported tank shapes use their corresponding geometry.

The calculator normalizes all dimensions before evaluating the formula, then converts the cubic result into practical liquid-volume units.

Worked example

Tank Volume Calculator Worked Example

2 m × 1.5 m × 1 m rectangular tank

Volume = 2×1.5×1 = 3 m³. Since 1 m³ equals 1,000 litres, the theoretical capacity is 3,000 litres before headspace or displacement is considered.

Result guide

Understanding Your Tank Volume Calculator Result

Treat the result as geometric capacity. If the tank is operated below the top or contains pumps, coils or internal structures, usable volume will be smaller.

Before you rely on the answer

Assumptions and Limitations

  • Internal dimensions represent the liquid space.
  • The selected tank geometry matches the vessel.
  • Headspace, internal displacement and inaccessible residual volume are excluded unless modeled.

Practical tip

Using This Result in Practice

For purchasing or process control, compare the geometric result with the manufacturer’s rated working capacity. Rated capacity is usually more useful than a hand calculation when the tank has complex internal geometry.

Related calculations

Useful Calculations to Continue With

If connected pipework contains a meaningful amount of liquid, add its hold-up with the Pipe Volume Calculator.

For a simple round vessel where only geometric volume matters, the Cylinder Calculator provides the same core formula directly.

Common questions

Tank Volume Calculator FAQ

Is tank capacity the same as usable volume?

Not always. Operating headspace, internal equipment and minimum liquid levels can reduce usable capacity below the geometric maximum.

Should I use outside tank dimensions?

Use internal dimensions for liquid capacity. Outside dimensions include wall thickness and therefore overstate internal volume.

How do I convert cubic metres to litres?

Multiply cubic metres by 1,000.