Conversion from Megaliters to US Dry pints

Information about the Megaliter (ML)

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.

Information about the US Dry pint (pt)

The United States dry pint is a unit of volume equal to 550.610471 millilitres, or 33.6 cubic inches. Its symbol is pt. It belongs to a separate American measuring system used for produce and grain rather than for liquids, and it is about sixteen per cent larger than the United States liquid pint of 473 millilitres.

Two parallel chains exist because two kinds of goods were once measured differently. Liquids descend from the wine gallon of 231 cubic inches, while dry goods descend from the Winchester bushel of 2150.42 cubic inches, a corn measure standardised in medieval England. Dividing the bushel by four gives a peck, by thirty-two a dry quart, and by sixty-four a dry pint, and none of those figures has any relation to the liquid chain.

Berries are where the unit is still met. Blueberries, raspberries and strawberries are sold in American markets in pint and quart baskets, and the basket is a dry measure. A pint of blueberries is therefore 551 millilitres of fruit, not 473, and a shopper comparing that basket with a pint of cream is comparing two different quantities under one name.

Nothing on a label resolves the ambiguity. Both are written pt, both are called a pint, and the word gives no clue as to which chain is meant. In practice the contents decide: if it pours, it is liquid measure, and if it is heaped, it is dry. That rule is reliable but it is nowhere written down, which is why converted American recipes so often disagree with one another.

Its existence is a survival from selling by bulk. Before cheap accurate scales, grain, apples, potatoes and shellfish were sold by filling a stamped measure and levelling it off, and the whole dry chain from bushel down to pint served that trade. Almost all of it has now been replaced by weight, and United States produce regulations increasingly specify pounds instead.

For conversion, the safest approach is to abandon the name entirely. A dry pint is 551 millilitres, a dry quart 1101, a peck 8.81 litres and a bushel 35.24. Writing the metric figure removes an ambiguity that the English word carries and cannot shed.

One United States dry pint equals 550.61 millilitres, 33.6 cubic inches, half a US dry quart, or about 1.164 US liquid pints.