Units of measurement

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Den (delvist) dansksprogede version af denne side findes her: Måleenheder

Length

Imperial units

Inch : 1 inch = 25,4 mm
Foot : 1 foot = 12 inches or 0,3048 meter
Yard : 1 yard = 3 feet or 0,9144 meter
Pole/Rod/Perch : 1 pole = 5¼ yards or the breadth of a team of 2 oxen.
Chain : 1 chain = 4 poles or the distance between the wickets in cricket.
Furlong : 1 furlong = 10 chains
Mile : 1 mile = 8 furlongs

Area

Imperial units

  • Acre: Originally an acre was the piece of land 1 chain wide and 1 furlong long, in other words 10 chain². This was the area that could be ploughed in one day with a medieval plough. The reason for the elongated shape is that it is very difficult to turn a team of oxen dragging a heavy plough, which is why they made the furrows as long as possible. This is probably also the reason that the communal fields in midieval times were divided into 'strips'.

Volume

Imperial units

Gill : 1 gill = ¼ pint or ½ cup
Cup : 1 cup = ½ pint or 2 gill
Pint : 1 pint = ½ quart or 4 gill
Quart : 1 quart = ¼ gallon or 2 pints
Gallon : 1 gallon = 4 quarts
Pin : 1 pin = 5.4 gal
Firkin : 1 firkin = 2 pin
Kilderkin : 1 kilderkin = 2 firkin
Barrel : 1 barrel = 2 kil

So in reality we use a binary measurement system. Of course the actual size depends on whether you start with an ale or beer gallon (282 in³ / 4.62 l), an imperial gallon (277 in³ / 4,54 l) or wine gallon (231 in³ / 3.78 l). Curiously an Ale Firkin is 8 gallons not 9 which is the beer firkin.

The conversion to ml in the table below are based on a UK teaspoon of 5.91938 ml, and a US teaspoon of 4.92892 ml. I know it doesn't make sense to talk about 'metric pints' and so on, but I included the calculated conversion to ml based on a metric teaspoon for the sake of completeness.

Unit Abbrev. Relational tsp ml (metric) ml (UK) ml (US)
Teaspoon tsp 1 5 ml 5.92 ml 4.93 ml
Tablespoon tbsp 3 tsp 3 15 ml 17.76 ml 14.79 ml
Cup C, c 16 tbsp 48 240 ml 284.13 ml 236.59 ml
Pint pt 2 c 96 480 ml 568.26 ml 473.18 ml
Quart qt 2 pt 192 960 ml 1136.52 ml 946.35 ml
Gallon gal 4 qt 768 3840 ml 4546.08 ml 3785.41 ml

The next table shows how many tablespoons and teaspoons a specific fraction of a cup is equivalent to, as well as the equivalent in ml, based on both the UK teaspoon (5.91938 ml) and the US teaspoon (4.92892 ml).

Fraction of a cup tbsp/tsp ml (UK) ml (US)
1/16 1 tbsp or 3 tsp 17.76 ml 14.79 ml
1/8 2 tbsp or 6 tsp 35.52 ml 29.57 ml
1/4 4 tbsp or 12 tsp 71.03 ml 59.15 ml
1/3 5 tbsp and 1 tsp 94.71 ml 78.86 ml
3/8 6 tbsp 106.55 ml 88.72 ml
1/2 8 tbsp 142.07 ml 118.29 ml
2/3 10 tbsp and 2 tsp 189.42 ml 157.73 ml
3/4 12 tbsp 213.10 ml 177.44 ml