Conversion from US Dry pints to Liters

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 Almost all of it has now been replaced by weight, and United States produce regulations increasingly specify pounds instead.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.

Information about the Liter (L)

The litre is a unit of volume equal to one thousandth of a cubic metre, or exactly one cubic decimetre. Its symbol is L, and the lower-case l is also permitted. It is not part of the International System of Units, but it is accepted for use alongside it, and it is almost certainly the most widely used volume unit in the world.

It was created by the French metric law of 1795 as the volume of a cube one tenth of a metre on a side. In 1901 it was redefined as the volume occupied by one kilogram of pure water at its densest, which sounds equivalent but is not: the water definition made a litre 1.000028 cubic decimetres, and for sixty-three years precise volumetric work had to state which litre was meant. The 1964 General Conference on Weights and Measures restored the cubic decimetre and the discrepancy vanished.

The symbol has its own small history. The lower-case l is easily mistaken for the digit one in many typefaces, a genuine hazard on a medicine label or a laboratory record, so in 1979 the capital L was approved as an alternative. Both are correct, and usage splits by country rather than by discipline, with North America favouring L and much of Europe still writing l.

Its everyday reach is enormous. Fuel, milk, paint, soft drinks and engine displacement are all measured in litres, fuel consumption in most of the world is stated as litres per hundred kilometres, and cooking outside the United States works in litres and millilitres. Medicine uses it for blood volume, roughly five litres in an adult, and for lung capacity, around six.

One relationship makes it exceptionally useful. A litre of water has a mass very close to one kilogram, because the kilogram was originally defined that way, so volume and mass can be swapped in the head for most practical purposes. Rainfall follows the same logic: one millimetre of rain on one square metre is exactly one litre of water.

Against imperial and United States measures it converts untidily, which is why drink sizes differ so visibly between markets. One litre is 1.76 imperial pints but 2.11 United States liquid pints, and 0.22 imperial gallons but 0.264 United States gallons, so a gallon means two noticeably different quantities depending on where the label was printed.

One litre equals 1000 millilitres, 0.001 cubic metres, about 0.264 US gallons, or about 0.22 imperial gallons.