It has been a long time since I discovered this nice Reddit thread about Metric vs Imperial system. There was an amazing comment listing all kinds of ounces, barrels, gallons and other crazy stuff, but recently it got deleted.
Thanks to Removeddit, a site that keeps deleted Reddit comments, I succeeded in recovering it. I believe there was a reason for deleting the comment by its author, and I hope that the author of this brilliant text wouldn’t mind - I just have to post it here so I can read it and laugh again and again:
There are four different ounces in use:
A Troy ounce is about 31.1 grams.
An Avoirdupois ounce is about 28.3 grams.
An Imperial fluid ounce is about 28.4 ml.
A US fluid ounce is about 29.57 ml.
This is related to the fact that a US fluid ounce is 1/16 of a US pint, while an Imperial fluid ounce is 1/20 of an Imperial pint, and an Imperial pint and a US pint are different. There are in fact three pints:
An imperial pint about is 568 ml, or 20 Imperial fluid ounces.
A US pint is about 473 ml, or 16 US fluid ounces.
A dry pint is about 551 ml, or
XXX dry fluid ounces... no, wait a "dry fluid ounce" doesn't exist, I wonder why.
This is in turn related to the fact that there are three gallons:
The Imperial gallon is defined in metric terms as exactly 4.54609 litres. It contains 8 Imperial pints.
The US gallon is defined as 231 cubic inches. It contains 8 US pints.
The dry gallon is defined as 1/8 of a US bushel. It contains 8 dry pints.
However, there are only two types of bushels:
The imperial bushel, equal to 8 imperial gallons.
The US dry bushel, equal to 8 US dry gallons.
There is no such thing as a US (non-dry) bushel, so if you want to convert a US gallon into the next higher US unit of volume, you have to use the beautiful correspondence:
- 1 US bushel = 9.30918 US gallons
The next higher up unit for measuring units is the barrel (thanks /u/AML86 for the reminder). There are at least ten different units called a barrel. Among these we will mention:
A dry barrel is 7056 cubic inches, which converts to a convenient ~3.28 dry bushels.
A barrel for cranberries (yes, really) is 5826 cubic inches , more or less ~2.71 bushels.
An Oil barrel is 42 US gallons.