Troy or Avoirdupois?

Jewelry Discussion
1

Greetings All,

This is slightly embarrasing, but here we go…I just looked up the
conversion between ounces and grams in McCreight’s “Complete
Metalsmith” and found that I didn’t know whether I was interested in
ounces troy or avoirdupois.

Can someone tell me the difference, and which would be the one I use
in the US for measuring precious metal?

thanks - Ivy

** Hanuman’s Response **

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2

ivy - an avoirdupois ounce is 35 grams while a troy ounce is 31.1 (+ a
smidgen) grams - which makes a troy pound = 12 ounces; troy weights go
on grains but grams are easier to remember. i seem to recall that the
whole system of precious material measurements was devised by
someone in a padded room with a mad-on at the world.

ive

3

Hello Ivy, I hadn’t thought about what avoirdupois ment until you
brought it up. My dictionary indicates that in English-speaking
counties, aviordupois weight is used for everything EXCEPT drugs,
precious stones, and precious metals - there are 16 oz/pound, with
7000 grains/ pound. Troy ounces would be appropriate for weighing
precious metal in the US - 12 oz/pound with 5760 grains to the pound.
(I guess a pound doesn’t necessarily equal a pound - or not all
pounds are equal!) Do you suppose we could make this a bit more
confusing? ;-} Judy in Kansas, where the temp is 70 and the day is
perfect… for a change.

4

Hi Ivy,

     I didn't know whether I was interested in ounces troy or
avoirdupois. Can someone tell me the difference, and which would be
the one I use in the US for measuring precious metal?

In the US, (& in most of the world) precious metals weights are
expressed using the troy system of measurement. The avoirdupois
system is used for just about everything else that’s sold in ounces
(not fluid oz.) & pounds.

The troy oz. is a little heavier than an avoirdupois ounce (1 troy oz
= 1.0971 avoir. oz).

To make matters more confusing, gold items, particularly chains, are
sometimes also sold by the gram. 1 troy oz = 31.1035 grams; 1 avoir
oz = 28.3495 grams.

Dave

5 
    This is slightly embarrasing, but here we go.....I just looked
up the conversion between ounces and grams in McCreight's "Complete
Metalsmith" and found that I didn't know whether I was interested
in ounces troy or avoirdupois. 

Can someone tell me the difference, and which would be the one I use
in the US for measuring precious metal?

The troy unit of measure is used to weigh precious metals. As
Americans, we tend to use avoirdupois method of weight, with 16 oz. to
a pound, however we still use troy weight for precious metals. These
two systems are antiquated, having come from methods which were used
in ancient days, which used either parts of the bodies to measure
distance (a rod was the length of a man’s fingertip to his nose), and
grains or bushels of wheat to measure weight, as these things were
commonly available to most people.

In the troy system, one grain equaled one grain of wheat. Twenty-four
grains of wheat equaled one pennyweight (the weight of a penny), 20
pennyweights equaled one troy ounce, 12 troy ounces equaled one troy
pound. One ounce avoirdupois equals .91146 ounce troy. I don’t know
what the avoirdupois method used as a measure, as the history teacher
never got around to that one. Maybe someone else out there has that
bit of trivia.

Just remember that when you’re ordering precious metals, it’s always
measured by troy ounces in the U.S. Base metals are usually ordered
by avoirdupois ounces, which is why an ounce of copper will weigh
(about 46%) more than an ounce of silver on a balance scale. However,
if you’re alloying your own metals, it’s more accurate to use the
European standards of weight in milligrams, grams, etc.

6

Hello Ivy,

This is slightly embarrasing, but here we go.....I just looked up the
conversion between ounces and grams in McCreight's "Complete
Metalsmith" and found that I didn't know whether I was interested in
ounces troy or avoirdupois.

Like they saying goes, “the only stupid question is the question that
is not asked.”

Troy units are used for measuring precious metals. Avoirdupois units
are used for postage, food and such.

Timothy A. Hansen

TAH Handcrafted Jewelry
web-site: http://www.home.earthlink.net/~tahhandcraft
e-mail: @Timothy_A_Hansen

7

G’day; the following is definitive - I just checked up in our
’Random House’ dictionary:- One avoirdupois ounce = 28.35 grams One Troy
ounce = 31.103 grams one gram = 15.432 grains.

Time the whole world changed to the metric system including the good
folk of the USA; (not that I’m a Frankophone - far from it!) we here
in NZ did nearly 30 years ago, and the kids don’t know what one is on
about if one mentions pounds or gallons! Cheers, –

John Burgess; @John_Burgess2 of Mapua Nelson NZ

8

Hello, What is really cool about Troy weight is that 1 gram is the
weight of 1 ml of water! Wax has basically the same specific gravity
of water. eg: 1 ml water = 1 cc wax. So if you have a disc in wax that
is 20mm in diameter by 3mm thick you can find the weight in sterling
silver like this…20/2 = Radius…so…10mm x 10mm x 3.14 (pi) x 3mm
= 942cm / 1000 = .942cc x 10.4 (specific gravity for sterling) =
9.7968grams. If you substitute the specific gravity of any given
alloy, you can ascertain the weight of any shape you can measure. The
metric gram is not arbitrary, the troy ounce is! I have heard that the
world metric standard meter is supposed to be in France somewhere. As
a caster I like that the troy/metric gram directly relates to volume.
I stay away from that pennyweight stuff even if it divides a troy
ounce nicely! John, J.A.Henkel Co.,Inc. Moldmaking Casting Finishing