HesapHanem

Tank Volume Calculator

Enter the tank diameter and length to compute its full cylindrical volume.

How it is calculated

The tank is treated as a full cylinder lying on its side or standing up: V = π × r² × L, where r is half the diameter. Diameter and length are entered in centimetres and converted to metres first, so the volume comes out in cubic metres. Litres are V × 1,000 and US gallons are litres / 3.78541.

Both inputs must be above zero. The result is the total interior capacity of a perfect cylinder, so measure the inside diameter, not the outside. Domed or conical ends, internal fittings and partly filled levels are not accounted for, which means a real tank usually holds a little more or less than the figure shown.

Worked example

A tank with an inside diameter of 120 cm and a length of 250 cm. Radius = 120 / 2 = 60 cm = 0.6 m; length = 2.5 m. V = π × 0.6² × 2.5 = π × 0.36 × 2.5 = 2.827 m³. In litres that is 2,827.4 L, and in US gallons 2,827.4 / 3.78541 = 746.9 gal.

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Common mistakes

  • Entering the diameter in metres or the radius instead of the diameter. The fields take centimetres and the full diameter.
  • Measuring the outside of the tank, which includes the wall thickness and overstates capacity.
  • Using the total to estimate how much liquid is in the tank. For a half-full horizontal tank the volume is not simply half of the length-based figure at a given height.
  • Confusing US gallons with imperial gallons; an imperial gallon is about 20% larger.

About this calculator

This calculator finds the full capacity of a cylindrical tank using V = πr²h — the diameter and length you enter give the radius and height of the cylinder — and converts the result into liters, cubic meters, and US gallons.

Farmers sizing water or fuel storage, industrial and process engineers, and homeowners with a cylindrical water or septic tank use it to know exactly how much a tank holds before ordering, filling, or specifying equipment around it.

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Comments (1)

  • Editorial team

    The result is for a full tank. If you lie the cylinder on its side and fill it only to a quarter of its diameter, it holds about 20 percent of the total, not 25, because the curved bottom is narrow. Fill levels in horizontal tanks are not linear, so a dipstick reading needs its own conversion. Is your tank standing or lying, and do you need partial-fill volumes as well?

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