| Cubic centimeters (cm³) | Gigaliters (GL) |
|---|---|
| 1 Cubic centimeter | 1 × 10-12 GL |
| 2 Cubic centimeters | 2 × 10-12 GL |
| 3 Cubic centimeters | 3 × 10-12 GL |
| 4 Cubic centimeters | 4 × 10-12 GL |
| 5 Cubic centimeters | 5 × 10-12 GL |
| 10 Cubic centimeters | 1 × 10-11 GL |
| 20 Cubic centimeters | 2 × 10-11 GL |
| 25 Cubic centimeters | 2.5 × 10-11 GL |
| 50 Cubic centimeters | 5 × 10-11 GL |
| 100 Cubic centimeters | 1 × 10-10 GL |
| Reference | Cubic centimeters (cm³) | Gigaliters (GL) |
|---|---|---|
| A teaspoon | 5 cm³ | 5 × 10-12 GL |
| A can of soft drink | 330 cm³ | 3.3 × 10-10 GL |
| A wine bottle | 750 cm³ | 7.5 × 10-10 GL |
| A bathtub | 150000 cm³ | 0.00000015 GL |
| An Olympic swimming pool | 2.5 × 109 cm³ | 0.0025 GL |
The cubic centimetre is a unit of volume equal to one millionth of a cubic metre, written cm³ and often abbreviated cc. It is the volume of a cube one centimetre on each side, and since the litre was redefined in 1964 it is exactly one millilitre. The two names describe the same quantity, but they belong to different trades and are not interchangeable in every context.
Engines are its most visible home. Motorcycle and small-engine displacement is quoted in cubic centimetres, so a 125, a 600 and a litre bike are named by the swept volume of their cylinders. Licence categories in much of the world are drawn on the same scale, with a 125 cc limit for learners in many European countries, which turns the unit into a legal boundary rather than a mere description.
Car engines cross over to litres at about a thousand cubic centimetres, purely for readability, so a 1998 cc engine is advertised as a two-litre. American practice used cubic inches for the same purpose well into the 1980s, and the conversion is worth knowing: 1000 cubic centimetres is 61 cubic inches, so a 350 cubic inch engine is 5.7 litres.
Medicine has deliberately retreated from the abbreviation. Syringes were once marked in cc and clinicians spoke that way, but handwritten cc can be misread as a unit symbol or as a pair of zeros, and medication safety bodies now place it on lists of abbreviations that should not be used. The instruction is to write mL instead, even though the quantity is identical.
Materials science keeps the unit for density. Grams per cubic centimetre is the standard way to state how heavy a substance is for its size: water is 1.00, aluminium 2.70, steel about 7.85, lead 11.34 and gold 19.3. Those numbers are memorable precisely because the cubic centimetre is small enough that everyday solids land between one and twenty.
Modelling and manufacturing use it for part volume. Computer-aided design reports the volume of a component in cubic centimetres, which converts directly to mass once a density is chosen and to material cost in additive manufacturing. It is the natural unit for anything that fits in a hand.
One cubic centimetre equals 1 millilitre, 1000 cubic millimetres, 0.000001 cubic metres, or about 0.061 cubic inches.
The gigalitre is a unit of volume equal to a billion litres, or one million cubic metres. Its symbol is GL. It is also exactly one cubic hectometre, which is the same quantity written in coherent SI form. It is the unit in which reservoirs, catchments and national water plans are counted, and it is where water measurement stops describing supply and starts describing landscape.
Dam storage is its principal use. Australian reservoir levels are published in gigalitres and as a percentage of a stated capacity in the same unit, so a city's water security can be read as a single number that changes week by week. Warragamba Dam, which supplies most of Sydney, holds a little over two thousand gigalitres when full, and the whole system a few hundred more.
Policy is written in it as well. The Murray-Darling Basin Plan set out to recover water for the environment in gigalitres, and every argument about that plan has been an argument about how many gigalitres should come out of irrigation and go back into rivers. Desalination plants are rated the same way: a large plant produces something like ninety gigalitres a year, which is a meaningful fraction of a city's demand.
Australians have an informal comparison for it. The volume of Sydney Harbour is taken as roughly five hundred gigalitres, and flood volumes, storage losses and river flows are described in harbours as casually as elsewhere they are described in swimming pools. Two thousand Olympic pools make one gigalitre, which is the more portable comparison for readers elsewhere.
The unit's identity with the cubic hectometre is worth holding on to. Spanish and Latin American hydrology publishes reservoir capacity in cubic hectometres, so a Spanish figure of 500 hm³ and an Australian figure of 500 GL describe exactly the same body of water, and any comparison between the two systems needs no arithmetic at all.
Above the gigalitre, water quantities pass to the cubic kilometre, which is a thousand of them, and are used for lakes, ice sheets and global budgets rather than for anything a government can manage. Below it, the megalitre takes over for individual farms, works and pipelines.
One gigalitre equals 1,000,000,000 litres, 1,000,000 cubic metres, 1 cubic hectometre, or about 264 million US gallons.