Conversion from Deciliters to US Gallons

Information about the Deciliter (dL)

The decilitre is a unit of volume equal to one tenth of a litre, or one hundred millilitres. Its symbol is dL, and the lower-case dl is common. Although the deci prefix has fallen out of use almost everywhere else, the decilitre is alive in two quite separate places: the Nordic kitchen and the clinical laboratory.

Scandinavian cooking is built on it. Swedish, Norwegian, Danish and Finnish recipes give flour, sugar, milk, cream and stock in decilitres, and a set of nested measuring cups marked in decilitres and fractions of one is standard kitchen equipment. Where an English recipe says a cup and an Italian one weighs the flour, a Nordic recipe asks for three decilitres, which is both faster and more repeatable than either.

Switzerland uses it for drink. Wine in a Swiss restaurant is ordered by the decilitre, so a glass is one or two and a carafe five, and the measure is printed on the glass. Because a decilitre is close to the volume of a modest wine pour, the unit gives customers an exact quantity rather than a description, which is what licensing law in several cantons requires.

Clinical chemistry is its other stronghold, and there it decides how a whole country reads its blood tests. Glucose, cholesterol and creatinine are reported in milligrams per decilitre in the United States, Japan, France, Italy and Spain, and in millimoles per litre in Britain, Canada, Australia and the Nordic countries. A fasting glucose of 100 milligrams per decilitre is 5.6 millimoles per litre, and the same person's result therefore looks entirely different depending on the laboratory.

Haemoglobin crosses the divide. It is reported in grams per decilitre almost everywhere, so a normal adult value of 13 to 17 grams per decilitre reads the same in most of the world. The decilitre survives in these places because a hundred millilitres of blood is a convenient reference quantity and because changing an established reporting unit risks misreading a result.

For scale, a decilitre is a small glass of water, half a mug of coffee, or the volume of a large egg and a half. It converts to 3.38 United States fluid ounces or 3.52 imperial fluid ounces, and to a little under half a United States cup, which is why converted Nordic recipes rarely come out in round numbers.

One decilitre equals 100 millilitres, 0.1 litres, about 3.38 US fluid ounces, or about 3.52 imperial fluid ounces.

Information about the US Gallon (gal US)

The United States gallon is a unit of volume equal to exactly 231 cubic inches, or 3.785411784 litres. Its symbol is gal US. It contains four quarts, eight liquid pints and 128 United States fluid ounces, and it is about a fifth smaller than the imperial gallon still used in Britain and Ireland.

It is older than its British rival. The figure of 231 cubic inches comes from the English wine gallon standardised in 1707 under Queen Anne, which was the common measure across the American colonies. When Britain abolished its several gallons in 1824 and replaced them with a single imperial gallon based on ten pounds of water, the United States simply kept the one it already had, and the two systems have diverged ever since.

Fuel makes it the most politically visible unit in American life. The price of a gallon of gasoline is quoted daily, watched by governments and used as shorthand for the cost of living, and vehicle efficiency is stated in miles per gallon on every window sticker. Because the American gallon is smaller, a car rated at 30 miles per gallon in the United States would be described as 36 in Britain, which is the same car and the same fuel.

The petroleum industry counts in a multiple of it. The barrel of crude oil is defined as 42 United States gallons, a figure fixed in the Pennsylvania oil fields in the 1860s when a 40-gallon barrel plus two gallons of allowance for leakage became the trade standard. Every published figure for world oil production and reserves rests on that convention.

Domestic quantities follow the same measure. Milk, paint, water for the garden, propane and swimming pool chemistry are all sold and dosed by the gallon in the United States, and a gallon of fresh water weighs 8.34 pounds against the imperial gallon's ten. That difference in weight is a useful check when a figure of uncertain origin needs to be identified.

Care with labelling matters when the two gallons meet. A liquid described simply as a gallon in an American document is 3.785 litres and in a British one 4.546, and nothing in the word itself distinguishes them. Writing gal US or specifying litres removes an ambiguity that has caused real errors in shipping, aviation and chemical dosing.

One United States gallon equals 3.785411784 litres, 231 cubic inches, 128 US fluid ounces, or about 0.833 imperial gallons.