Measure the tank’s internal length, width, and height in metres
Use the formula: Capacity in cubic metres = Length × Width × Height
Convert cubic metres to litres by multiplying by 1,000
For a cylindrical tank, use the formula: Capacity in cubic metres = π × radius² × height
Convert the result to litres by multiplying by 1,000
For a spherical tank, use the formula: Capacity in cubic metres = 4/3 × π × radius³
Convert the result to litres by multiplying by 1,000
For an irregular tank, divide it into simple shapes, calculate each volume, then add them together
Subtract any space not filled with water if needed
Use the internal dimensions only, not the external dimensions