Cylinder Tank Volume Calculator: Formula and Examples

A cylinder tank volume calculator finds the space inside a cylindrical tank from its diameter and length or height. Enter both measurements in the same unit to get the tank’s geometric volume, with a conversion to common units for easier comparison.

Formula

The volume of a right circular cylinder is the area of its circular end multiplied by its length or height:

V = πr²h = π(d ÷ 2)²h

• V is volume, in cubic units such as cubic metres (m³) or cubic feet (ft³).
• r is the cylinder’s internal radius, half its internal diameter, in the same length unit as h.
• d is its internal diameter.
• h is the cylinder’s straight length when it lies horizontally, or its height when upright.
• π is approximately 3.14159265.

The calculator takes diameter and length or height in metres. It reports cubic metres, litres, and US gallons. One cubic metre equals 1,000 litres and approximately 264.172 US gallons. A US liquid gallon is not the same size as an Imperial gallon; one US gallon is approximately 3.785 litres, while one Imperial gallon is approximately 4.546 litres.

Worked Example

Using the calculator’s default values, the internal diameter is 1 m and the length or height is 1 m. First find the radius:

r = d ÷ 2 = 1 ÷ 2 = 0.5 m

Then calculate the cylinder volume:

V = π × 0.5² × 1 = 0.785398… m³

Rounded to three decimal places, the result is 0.785 m³. Converted to litres, the unrounded volume is 0.785398… × 1,000 = 785.4 L. Converted to US gallons, it is 0.785398… × 264.172052 = 207.9 gal. The calculator rounds each displayed result to the precision shown in its block.

How to Measure a Cylinder Tank

Use the tank’s internal dimensions if you want its capacity. The outside diameter includes the wall thickness, so using it can overstate the amount of space available inside. If only the external dimensions are accessible, subtract the wall thickness on both sides to estimate the internal diameter; treat the result as an estimate, especially for thick-walled vessels or tanks with a lining.

• Diameter: Measure straight across the circular interior through its centre, not around its circumference.
• Length or height: Measure parallel to the cylinder’s central axis, between the inside end surfaces.
• Units: Convert both measurements to the same unit before calculating. For example, 80 cm is 0.8 m; do not combine 80 cm with a length of 2 m without conversion.
• End shape: Check whether the ends are flat, domed, or otherwise formed. The basic cylinder formula assumes flat ends and does not include extra volume in a dome.

For a horizontal tank, its axis length is the cylinder’s length. For an upright tank, use its vertical height. The formula is the same in either orientation; the tank’s position does not change its full geometric capacity.

Using the Result in Practice

The answer is the tank’s theoretical internal volume when completely filled to the cylinder’s full boundaries. It is useful for comparing tank sizes, estimating storage capacity, or checking an approximate liquid quantity. A result in cubic metres is often convenient for larger tanks; litres or gallons may be easier to interpret for smaller containers.

Full capacity is not necessarily the usable amount. A tank may need headspace for expansion, ventilation, safe operation, or to avoid overflow. Internal fittings, pipes, baffles, sediment, and irregular end shapes can also reduce the liquid volume. For a level reading in a partly filled horizontal tank, multiplying full capacity by the fraction of its length covered is generally not accurate: the liquid’s cross-sectional area changes as its depth changes.

Common Errors and Formula Limits

• Using radius as diameter: If you measure the radius, enter twice that value as the diameter. Confusing them changes the computed result by a factor of four because the radius is squared.
• Mixing units: Keep diameter and length in the same unit. If both are entered in centimetres, the formula returns cubic centimetres; convert the result as needed (1,000 cm³ = 1 L).
• Measuring around the tank: Circumference is not diameter. If circumference C is known, first find d = C ÷ π, then use the cylinder formula.
• Rounding too early: Keep extra digits during intermediate steps and round the final result. A rounded display is an approximation, not a measurement guarantee.
• Assuming every tank is a perfect cylinder: This formula does not directly model tapered tanks, rectangular tanks, irregular interiors, or additional volume in curved end caps.

When a tank has rounded ends, calculate the cylindrical middle separately and account for the ends using a shape-appropriate formula or manufacturer dimensions. A common idealized hemispherical end has volume 2πr³/3; two hemispherical ends together make one sphere, with volume 4πr³/3. Actual formed ends may not match that ideal geometry.

Frequently Asked Questions

How do I calculate the volume of a cylinder tank?
Multiply π by the square of the internal radius and by the tank’s internal length or height: V = πr²h. If you know diameter instead, halve it to get the radius.

Does a horizontal cylinder have a different volume from an upright one?
No. Orientation does not alter the full volume. Use the same formula, with the cylinder’s axis length as h. The amount of liquid in a partially filled tank, however, depends on the liquid depth and orientation.

How many litres does a cylindrical tank hold?
Calculate volume in cubic metres and multiply by 1,000 to get litres, or calculate in cubic centimetres and divide by 1,000. The answer is theoretical capacity and may exceed the recommended usable fill.

Can I use outside measurements?
You can use them for a rough estimate, but they produce an overestimate of internal capacity because the tank walls take up space. Use internal diameter and internal length when available.

Why does my measured tank hold less than the calculator says?
The tank may have thick walls, curved ends, internal equipment, a fill limit, or dimensions that differ from the measurements used. The calculator models a simple, full cylinder and does not account for those details.

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in d | Diameter | m | 1 | 0
in h | Length or height | m | 1 | 0
out v | Cylinder volume | m³ | pi * (d / 2)^2 * h | 3
out liters | Volume | L | v * 1000 | 1
out gallons | US gallons | gal | v * 264.172052 | 1