| Megaliters (ML) | Cubic meters (m³) |
|---|---|
| 1 Megaliter | 1000 m³ |
| 2 Megaliters | 2000 m³ |
| 3 Megaliters | 3000 m³ |
| 4 Megaliters | 4000 m³ |
| 5 Megaliters | 5000 m³ |
| 10 Megaliters | 10000 m³ |
| 20 Megaliters | 20000 m³ |
| 25 Megaliters | 25000 m³ |
| 50 Megaliters | 50000 m³ |
| 100 Megaliters | 100000 m³ |
| Reference | Megaliters (ML) | Cubic meters (m³) |
|---|---|---|
| A teaspoon | 0.000000005 ML | 0.000005 m³ |
| A can of soft drink | 0.00000033 ML | 0.00033 m³ |
| A wine bottle | 0.00000075 ML | 0.00075 m³ |
| A bathtub | 0.00015 ML | 0.15 m³ |
| An Olympic swimming pool | 2.5 ML | 2500 m³ |
The megalitre is a unit of volume equal to one million litres, or one thousand cubic metres. Its symbol is ML. It is the working unit of water management: irrigation entitlements, treatment works capacity, farm dams and the trading of water rights are all counted in megalitres, because the quantities involved are far too large for litres and awkwardly small for cubic kilometres.
Australia has made the most of it. Irrigation water in the Murray-Darling Basin is held as entitlements measured in megalitres, seasonal allocations are announced as a percentage of those entitlements, and the resulting rights are traded on an open market where prices are quoted in dollars per megalitre. That market is among the largest of its kind in the world, and every price in it is a price per million litres.
British water utilities use it for throughput. A treatment works is rated in megalitres per day, distribution zones are balanced in the same unit, and leakage is reported as megalitres lost daily across a network. Because a large city consumes several hundred megalitres a day, the unit keeps national and regional figures in three or four digits rather than in unreadable strings of zeros.
A familiar object fixes the scale. An Olympic swimming pool of fifty metres by twenty-five, filled to two metres, holds 2500 cubic metres, which is two and a half megalitres. Journalism uses that comparison constantly for reservoir levels and flood volumes, and it works precisely because the pool and the unit are within a factor of three of each other.
On farms the unit describes storage. An Australian farm dam might hold anything from five to fifty megalitres, an on-farm irrigation season is planned in megalitres per hectare, and evaporation losses from open storage are estimated the same way. Sewage treatment, industrial process water and mine site water balances all follow.
Its one hazard is typographic. In the correct symbols, mL is a millilitre and ML is a megalitre, and the two differ by a factor of a thousand million. A document that is careless about capitals can therefore turn a laboratory volume into a reservoir, which is why water and clinical writing both insist on the case being right.
One megalitre equals 1,000,000 litres, 1000 cubic metres, about 264,172 US gallons, or about 220,000 imperial gallons.
The cubic metre is the SI unit of volume, written m³. It is the volume of a cube one metre on each side, and because the metre is a base unit, every other volume unit in the system is derived from it. It holds a thousand litres, and a cubic metre of fresh water has a mass of very nearly one tonne, which is the single most useful fact about it.
Utilities are billed in it. Domestic water meters almost everywhere record consumption in cubic metres, and a household of four uses somewhere between 100 and 200 of them a year. Natural gas is metered the same way and then converted to energy for billing, because the heat released by a cubic metre of gas depends on its composition and has to be corrected for temperature and pressure at the meter.
Construction orders materials by it. Ready-mixed concrete is sold and delivered by the cubic metre, a standard truck carrying six to eight; excavation and earthworks are priced per cubic metre moved; and sawn timber, aggregate, topsoil and bark are all traded the same way. Because a cubic metre of concrete weighs about 2.4 tonnes, the unit also decides what a lorry or a crane can carry.
Freight uses it in a more subtle way. Shipping and removals quote volume in cubic metres, and air freight charges by whichever is greater, the actual mass or a volumetric mass calculated at a fixed ratio, commonly 167 kilograms to the cubic metre. Light bulky cargo is therefore priced by the space it occupies rather than by what it weighs, and the whole calculation runs on this unit.
Environmental measurement lives here too. River flow is given in cubic metres per second, reservoir capacity in millions of cubic metres, air quality as micrograms of pollutant per cubic metre of air, and ventilation as cubic metres per hour. A room four metres by five with a ceiling at two and a half holds fifty cubic metres of air, which is the sort of figure ventilation standards are written against.
Against imperial and United States units it converts to 35.315 cubic feet or 1.308 cubic yards. The cubic yard matters most in practice, because American concrete and excavation are ordered in it, and the two units are close enough that a mistaken figure looks plausible while being a third out.
One cubic metre equals 1000 litres, about 35.315 cubic feet, about 1.308 cubic yards, or about 264.2 US gallons.