The cubic metre (or cubic meter; US spelling) is a unit of volume and is derived from an SI unit with the symbol m³.
1 cubic metre is exactly 1000 litres. It is also ≈ 6.29 barrels, ≈ 220 imperial gallons and ≈ 35.3 cubic feet.
1 cubic metre of water in normal conditions (≈4 °C) weighs exactly 1000 kg (or 1 tonne).)
The cubic metre is the unit used to measure water usage and often water bills are broken down into how many m³ has passed through the property / business.
The cubic millimetre (or cubic millimeter; US spelling) is a unit of volume and is derived from an SI unit with the symbol mm³.
One cubic millimetre is defined as the volume of a cube with sides one millimetre in length. It is the same as a microlitre. It is equal to 0.000000001m³.
There are 1 billion cubic millimetres in a cubic metre.