Why are there three different measurements called the ounce?

It seems like a bad system to use the same name for three different units. There is a fluid ounce, a troy ounce( only used for precious metals)and the avoirdupois ounce(1/16 of a pound). How did this come to be?

Historically there have been many other versions of the ounce. Same is true for pound. Before international standardization there was no single authority to define them so each industry, country, etc used local versions. Some of them are still in use, others have dropped by the wayside.


Well actually there is for every day use just one. Nobody uses Troy measurements in daily use. And the liquid ounce of water equals 1.04 weight ounces. Nice coincidence and I use it fairly often.

Of course there are still many anomalies in everyday use. American gallons vs UK gallons; a ton has too many varieties to list here.

When I was at school, I had to learn my 16 times table thanks to the oz/pound ratio.

There are two different fluid ounces, even if the imperial fluid ounce has mostly gone away because of conversion to the metric system. The imperial fluid ounce is about 28.4 ml (and not by a “nice coincidence” is exactly one ounce of water); the American fluid ounce is about 29.6 ml. The difference is connected to the difference between imperial and American pints, quarts and gallons.

The reason all our traditional units have all these odd conversion ratios and values is that nobody sat down and designed a rational system. Nobody said, “Lets make a unit called the foot, and make 5820 feet into a unit called the mile.” Rather, feet and miles were used in totally different ways, and nobody converted feet to miles, they always worked in one unit or another. Feet if you were a carpenter, miles if you were a soldier (a mile is how far a legion should march in an hour) or surveyor.

Different countries, regions, industries, or guilds had different versions of a “standard” unit. There was no precise definition of an ounce, which didn’t matter as long as the people using the unit for calculation agreed on what the value of an ounce was. So it’s not that there are three or four versions of an ounce, there used to be hundreds, and as national and international trade increased those versions became mostly harmonized, until we’re left with only a few surviving standard versions.

There’s a fairly simple way to do away with even these outdated fossilized relic units of measure like hogsheads and furlongs and cubits in favor of a global universal and logical system, you may have heard of it.

Don’t get me started on carats, karats and carrots.

I question the mile as time/distance. A Roman mile was “mille passus” a thousand paces. Pace according the the Roman style was from where your left foot left the ground to where it touched
it again - we would call this 2 paces. Roman mile longer than English?

To do 1000 paces per mile would require a stride length of over 5 feet. That’s more of a running stride. Walking pace would have a much shorter stride so 1000 paces would be two steps.

The origin of the word “ounce” (and “inch”) is from the Latin word meaning "one-twelfth part, and in fact the Troy Ounce arose as 1/12 of a pound, not the 1/16 that came into use, when the term was broadened to imply whatever fractional unit of a measure seemed needed.

A Fluid Ounce is the same fractional part of a Pint, as the Ounce is to the Pound, and a fluid Pint in fact weighs One Pound.

Don’t forget the Ounce, and alternate name for the Central Asian Snow Leopard.

No it was shorter. It was as stated really 1000 paces (mille passum as I’ve always heard it, but passum seems singular to me). This was 5000 Roman feet or a bit more than 4800 modern English (O American) feet. As I recall the English lengthened the mile by statute (hence statute mile) in Elizabethan times to make it exactly 8 furlongs giving us this strange 5280 feet rather than 5000 feet.

I’ll also note that the mile in the U.S. is now defined in terms of the meter. It is exactly 1609.344 meters except that the U.S. survey mile is about 3 millimeters longer. I suspect they simply didn’t want to have to update all the surveys.

1mph? That is terribly slow probably about a third of what a guy carrying a backpack can average if they are in good shape.

And carets. :slight_smile:

US pints that is.

I learned the following mnemonic for the relationship:

A pint a pound,
The world around.

When I lived in New Zealand, which used Imperial pints, I found out “the world around” part wasn’t true. Because there

A pint of water
Weighs a pound and a quarter.

I don’t think it’s a “coincidence”.

IIRC, the Imperial fluid ounce is something like “the volume of water with a mass of 1 ounce at a temperature of 62 degrees Fahrenheit,” while the “American” fluid ounce is 231/128 cubic inches (i.e. 1/128 of a US gallon, defined as 231 cubic inches).

Ah, excellent! Something new every day. :slight_smile:


In Latin, mille generally takes the genitive plural (passuum), though it can also be an indeclinable adjective modifying any case. In the plural, it is always the neuter noun milia.

1000 paces = *mille passus *(nom.) or mille passuum
2000 paces = duo milia passuum

Logically, it should be mille passī, but I suspect that it’s mille passum because both function as neuter adjectives: the thousand-pace [unit].

::brain explodes::

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