| Reference | Quarts (qt) | Gills (gi) |
|---|---|---|
| A teaspoon | 0.00439938 qt | 0.0351951 gi |
| A can of soft drink | 0.290359 qt | 2.32288 gi |
| A wine bottle | 0.659908 qt | 5.27926 gi |
| A bathtub | 131.982 qt | 1055.85 gi |
| An Olympic swimming pool | 2199692 qt | 17597540 gi |
The quart in the imperial system is a unit of volume equal to exactly 1136.5225 millilitres. Its symbol is qt. It is two imperial pints and a quarter of an imperial gallon, and its name says so: quart comes from the Latin quartus, a fourth. It sits between the pint and the gallon and, in Britain, it has lost to both.
Its decline is the clearest case of a unit being squeezed out from both sides. The pint survived because it is the legal measure for draught beer and because a person can hold one; the gallon survived in fuel economy figures. The quart is neither drunk nor driven, so nothing kept it in daily speech, and British shops now describe the same quantity as a litre or as two pints.
In the United States the same name is thriving. A United States liquid quart is 946 millilitres, and milk, cream, stock, ice cream, paint and motor oil are all sold in that size. An engine oil change is quoted in quarts, five being typical for a car, and the quart carton is one of the most recognisable objects in an American kitchen.
That American survival owes something to the litre. A United States quart is only five per cent smaller than a litre, so shelf sizes barely changed when Canadian and international products moved to metric, and a shopper comparing a quart with a litre is comparing almost the same thing. The imperial quart is thirteen per cent larger than a litre, which made the same substitution less comfortable in Britain.
The dry measure adds a further complication in the United States. A dry quart is 1101 millilitres against the liquid quart's 946, and it belongs to a separate chain used for berries, produce and grain. Nothing on a label distinguishes them, so the same word describes two different quantities depending on whether the contents pour or not.
For conversion, the imperial quart is 1.1365 litres and the United States liquid quart is 0.9464. The rule of thumb that a quart is roughly a litre is safe in America and about a seventh out in Britain, which is exactly the kind of margin that turns a recipe or a chemical dilution wrong without looking obviously wrong.
One imperial quart equals 1136.5225 millilitres, 2 imperial pints, 0.25 imperial gallons, or about 1.201 US liquid quarts.
The gill is a unit of volume equal to a quarter of an imperial pint, or exactly 142.0653125 millilitres. Its symbol is gi. It is five imperial fluid ounces, and it sits between the fluid ounce and the pint in the old British liquid chain. Its name is pronounced with a soft g, so that it sounds like the name Jill, which surprises most readers who meet it only in print.
For most of the twentieth century it governed the British pub. Spirits were served in fractions of a gill, and the fraction varied by region: a sixth of a gill in England and Wales, a fifth in Scotland, and a quarter in Northern Ireland. A traveller ordering the same drink in three cities therefore received three different quantities, all legally correct and all described by the same words.
That system ended in 1995, when the United Kingdom replaced the gill fractions with metric measures of 25 or 35 millilitres, each establishment choosing one and displaying which. The change was less disruptive than it looked, because a fifth of a gill is 28.4 millilitres and a quarter is 35.5, so the new measures sat close to the old ones and the drinks barely changed size.
Cookery kept it longer than the law did. British and Irish recipes written before the 1970s call for a gill of cream, stock or milk, and the quantity is a quarter pint, which is 142 millilitres. Anyone working from an inherited recipe book meets the word regularly, and the conversion is one of the few worth writing on the flyleaf.
The American gill is a different quantity again. It is a quarter of a United States liquid pint, therefore four United States fluid ounces or 118.3 millilitres, about a sixth smaller than the imperial gill. It appears in old American recipes and in the occasional bar manual, and the same caution applies as with the pint: the name says nothing about which system is meant.
Today the gill survives in dialect, in historical writing and in the specifications of glassware sold for period use. It is one of the clearest cases of a unit outliving its own function, kept alive by cookbooks and by the memory of how a drink used to be poured.
One imperial gill equals 142.065 millilitres, 5 imperial fluid ounces, 0.25 imperial pints, or about 1.201 US gills.