Ring sizes

Hello All,

Coming from a machinist background I am admitedly a bit fussy about
dimensions/tolerances. I’ve been trying to locate the definitive
“Source” for ring size dimensions (specifically U. S.). And. can’t
seem to find it. There seems no shortage of charts showing dimensions
and conversions between the many different standards, but if you
examine the numbers closely, there is often slight variation (enough
to really bug me). Does anyone out there know where these numbers
originally came from? Their formula? Thanks in advance.

Jeff McWhinney

Hi Jeff,

Somehow or other, I ended up with a machinist’s background. Given my
druthers, I’d have rings sized to tenths.

Unfortunately, I don’t think there is a canonical list for ring
sizes. I’ve been looking for years, and all the charts I’ve found
either conflict with each other, or have traceable errors to an
earlier list. What’ll really blow your mind is that sometimes the ID
of the sizing ring for a given size can be as much as 25-40 thou
different than the OD of a mandrel for the ‘same’ size. I’ll bet you
even money that if you mike three different mandrels in your shop
for a given size, all three will come back with different OD’s.
Standardization? Ha! measurements by millennia.

On the other hand, it’s important to remember several things:

(A) humans change size. Even if you do mike the finger accurately in
the morning, an hour later, it’ll be a slightly different size. And a
third size by dinnertime. So the best you can hope for is
’comfortable’, which can often be ± as much as 20-30 thou.

(B) Fingers aren’t really round. They’re sort of square-ish. So
getting an ‘accurate’ ID on a round band really won’t do much good
in terms of the levels of accuracy you’d normally run into.

© The width of the band radically effects how its fit is perceived
by the wearer. The wider it is, the tighter it feels, regardless of
the actual ID. Some of the wide (6mm+) rings take about a half-size
jump to get them to feel right. (a “6” turns into a 6.5, for

Yes, in a perfect world, I’d like to be able to say that all “size
7” rings start out at the same ID, to aid in fitting, but you can’t.

Most of us just develop strategies to deal with the flutter in the

Mine is to get a ring that does fit, regardless of the printed size,
and then measure the ID of that ring, and make the next one to match.
Exactly. So if it came out at .788", the real ring will be.788 thru
the bore, with a bit of chamfering around the ends to make it
comfortable. Of course, that only works if you’re doing one-off
customs. For production pieces, find a mandrel that seems to give you
accurate sizes, and run with that one mandrel being "the’ sizer. A
few (tens) of thou of variation in the ID measurement won’t make much


From our archives…

Determination of Ring Sizes
by Prof. Dr. Erhard Brepohl

A ring fits well when it is no longer felt on the finger. If in the
course of time the size of the finger changes or if the ring is to
be fitted for another wearer, a sizing of the ring is necessary. The
first step is to determine the finger size, which is done with a
ring sizer, a set of about 30 steel rings in graduated sizes, figure
13.1. If the customer has a comfortable ring to use as a guide, its
size is measured on a graduated ring stick…

Fingers aren’t round, neither are they specific sizes. One finger
will be different from a cold dry week to warm wet one. Let go of
your hangup and just take your measurements off your favorite
mandrel. If it’s white gold it doesn’t matter what size you make it
she will change her mind right after you plate it and you will be
resizing it again. That’s my take.

You’re wasting your time chasing an artificial ideal. Hope that
helps. SD

Hi Jeff,

I have found the fuzzy and contradictory conventions of ring sizing
very confusing. I now only use the ISO system which is simply the
internal circumference of the ring in millimetres. The crucial thing
for me is that I have a set of 36 ISO rings a calibrated mandrel. If
I am making a ring to size I measure the client’s finger and use the
matching mandrel to make the ring.

I do have a conversion chart to give the equivalents in the US
number sizes and the British letter ones but as you can see the ISO
system scale is a great deal more even and precise

I don’t make a lot of rings now, so maybe I am missing something in
this discussion, but when I do, I ignore any number graduation on
either the sizing ring or mandrel. I have a set of wide and a set of
narrow ring sizers. Physics dictates that a wider ring will have to
be a bit bigger for the same finger than a narrower ring. Once they
find a sized ring that fits, I note the number for reference only
and then run it up the steel ring mandrel and get it tight in place,
mark both sides with a sharpie and make the ring to fit this spot. A
wide ring usually has to be stretched a bit, but I try to leave the
finished ring on the small side as stretching is a lot easier than
sizing down. Please note that I make fabricated silver rings with
freeform stones that are usually bezel set. They can be rolled or
hammer to make them larger in size and then refinished. This process
may not work so well for faceted stone rings made from cast or
stamped pieces that are assembled to size as rolling or hammering to
size may distort the ring. I agree that a well made and sized ring
should not be felt. But, like any piece of adornment, this may take
some getting used to. I caution my customers to please come back if
they decide that it doesn’t feel right or fails them in any way.
This rarely happens, not because I am such a great ring maker, but
because they just get used to the feel. There was a time when I made
a lot of little rings. I would take about six feet of 14 gauge wire
and wrap it up a tapered wooden mandrel, cut the coil lengthwise,
solder the seam, apply whatever forging design and finish made sense
and then display them in a bowl that customers could go through
until they found one that fits. The conversation was usually: “Do
you have a size 6?” “Probably, just go through until you find one
that fits.” I would remind them that they have ten opportunities to
buy a ring on their hands and ten on their feet, so have a good
time. There were many shows were I made a lot of money on little
rings, but I don’t do shows any more. My two cents. Rob

Hi Jeff,

For reasons best known to the great gods of Orchid, sometimes bits
of my posts disappear. In most cases it doesn’t really matter much,
but in this case.

for a given size, all three will come back with different OD's.
Standardization? Ha! measurements by millennia. 

What I meant to say was "Standardization? Ha! Remember: this field
predates interchangeable parts and standard measurements by
millennia. "


One of the things that makes ring sizing problematic from time to
time is that no two rings fit the same. Someone may wear a size 5
narrow engagement ring and find that a size five matching band is too
big, even on the same finger. Or another similar and very common
scenario, a wider band at size five may be too small, but the same
width ring with a heavier or taller top may roll around
uncomfortably. This kind of thing isn’t at all uncommon.

Different people like their rings to fit differently too. Some want
to almost have to screw it on and off (there goes the finger in the
mouth, darn it - I hate that!), while others get claustrophobic at
the slightest resistance. Some people have large fingers, but want to
have small fingers and really don’t want to hear that they don’t wear
the same size they did in college. I’m reminded of what my
mother-in-law used to say about her shoe size - “I wear a size six,
but a seven feels so good I get an eight.”

Then we sometimes encounter the “princess and the pea” syndrome,
where a size five fits perfectly during the design phase, but is way
too small when delivered. By “way too small”, she means that she
needs it to be larger, but a size 5 1/4 is just a little on the large
size. So I tell them I’ll make it a 5 3/32. Funny how it works, but
that often does the trick. Sometimes, I guess they just want to watch
the monkey dance, so to speak. Not so funny when we start at size
five which is too small, go to a size 5 1/4, which is now too big, go
down to a 4 3/4, which is way too small, and end up going back to a
size 5 which now fits perfectly. Until next month, when it’s too
small again. Dance, monkey dance.

I find that the most successful approach is to select a size that
will just barely fit over the knuckle and go with that. If it’s too
loose and rolls around, I add sizing beads. If it’s too tight after a
few days or weeks trial run, it has to go up. I also make sure each
and every person I work with on ring sizing is told that ring sizing
is not an exact science, and that it is not at all uncommon that the
ring size will have to be tweaked. Remove the element of surprise and
you remove the potential for an angry customer. Usually.

Dave Phelps

I too have attempted to trace the origins of ring sizes, but with
little success. I’m in the UK and Some years ago, after carefully
measuring a number of (UK) ring sticks and gauges, concluded that the
most likely origins were associated with the Imperial measurement

I noticed that the diameter of size “C” was very close to 1/2"; some
measurements were a little less, some a little more, and size “Z”
was very close to 55/64". Since there are 23 ring sizes between
“C"and"Z”, I concluded that this was possibly the origins of the UK
system, where the sizes increment by 1/64".

Comparing this with the “official” table published by the “Jewellery
Advisory Centre, London”, gave a very good correlation. The JAC
gives size “C” as 0.5060" (just 6 thou more than 1/2"), and size “Z”
as 0.8625" (just 3 thou more than 55/64").

Ring sizes were devised long before the Imperial measurement system
was rigorously defined, and it seems likely that, since there was
never a pressing need for a precise (Engineering) standard, there was
no requirement for a jewellers Whitworth to devise one, so we ended
up with a whole load of approximations based on local archaic
definitions that the JAC finally reduced to the table they published.

My theory is probably fanciful, but it seems very plausible to me.
And it works well in practise.

Some years ago I created the chart at
http://www.ganoksin.com/gnkurl/ep8197 [PDF file]

It is based on the table published by the JAC, but I personally use
the 1/64" incremental system with good consistent results.

Regards, Gary Wooding

Hi All

Ring sizing is a real pain. What fits well in the morning may be too
tight later in the day.

Which is why I make few rings to order. I make them and if they fit

When I make stone set rings to order I get the client to wear the
ring band for a week before I put in the bezel set stone. Then I can
size it up or down.

Also NEVER let a customer take their own ring size they always get
it wrong.

You must take the size yourself.

Also different races have various sized fingers. Asian ladies have
very small fingers, Europeans have bigger and Pacific Islanders are
much bigger. So I make stock from K to Z plus.

Jewellery stores sell standard size rings L, M, N, O then charge to
size the ring to fit I have many customers tell me they cannot get
rings to fit be it a K or a Z. So I get many sales from outside the
NORMAL range of sizes.

Also I have noticed that with gem set rings ladies will try the ring
on different fingers to get it to fit.

I have found these posts very interesting, getting the design and
size right is very difficult.

So Newbies make your rings and if they fit good. Making to order is
very complicated and difficult.

Keep notes on ring sizes and band profiles because shank profiles
make all the difference.

have fun and service the customer.

Hi All,

Thanks for all the responses. No shortage of real experience here.

My question was on size though and not fit. I get that fingers
shrink/swell and that ring shape/width are part of the calculation.
Its why upon receivinga ring order, I send out 3 Delrin test (dummy)
rings- the size requested and 1/4 smaller and larger. I make the
test rings the exact cross section of the ring ordered and tell the
customer to wear the most comfortable one for however long they need
before they have 100% confidence its right. Most of mywhat I make
are mens wedding rings and a lot of my customers have never worn a
ring before so they really appreciate this step. I had a nice guy in
England take 2 1/2 weeks to make his decision, but in the end he
"absolutely loves" his ring.

Back to size. mostly I want to be accountable. If I tell someone I’m
making them an 11, I want it to be an 11. So yeah, I’m a bit
obsessive on details, but its one of the things that many guys
appreciate about my work. They are fellow obsessives, my brothers.
And, I love making them happy.

Jeff McWhinney

Ring sizes?

I learned so many years ago never to use a mandrel where the
jewellers are using it, why? The bench jeweller will have a mandrel
that is constantly being used, so what happens? It will & might get
worn down, therefore you might have a wrong size at the 'retail’

Your size counter #7 might end with a bench-jewellers 6.75…got it
now sized & polished and find out a definite. woops! Money & time
lost!!! Keep that special mandrel upfront!!! But never let anyone
’hit it’ with hammers or let it get touched by anyone but those with
the customer.

No client wants to see “their beautiful” ring sliding on a steel
pole with dents in it!..yuk! Suggestion for you, keep a ‘plastic ring
mandrel’ just to be used for counter-sizing. If that gets worn down
by 1/4 size, scrap it. now! Buy a new one. all you’ll now have are
happy clients!!

Gerry Lewy

I see a lot of discussion of ring size origin and fit. How about how
and where we measure the rings size. Here are several solutions that
helped me in retail and in my school. In the retail situation it
reduces our reworks by 70%. That’s a big jump. First we checked all
of our mandrels to see if they match. we used a digital caliper and
compared US size 5 to 12 including half sized. Out of 14 8 matched.
we replaced the 6 with matching mandrels. Problem one solved. We
then found that many of our ring sizers were 1/8 to 1/4 size off
compared to our mandrels. This included wide, narrow, comfort-fit
and tapered rings sizers. Our solution was simple, I ground off the
numbers. This way any sales associate or jeweler needed to confirm
the ring sizer with a confirmed mandrel. Later as we got new ring
sizers there was no need to grind the numbers off but rather
everyone was used to checking against the mandrelsin all situations.
The last major issue was wheredid staff read the the measurement. I
was taught to read it in the middle of the ring, but soon realized
that that was not accurate and would change as the ring got wider.
I’ve heard jewelers defend it saying that is how themandrels were
made and that’s how they compensated for wider rings. Bull. A 6mm
flat sided ring measured in the middle might be size 6 where a 10mm
flat sided ring measured in the middle might be a size 5 3/4. How is
this accurate? Flat sided rings, especially the interior shank
should be measured like a pipe. At the bottom edge of the ring. It
is the same measurement allthe way through the pipe (ring) be it 6mm
or 60mm. We measured comfort fit rings in the middle since they have
a radius-ed inner shank and actually have a smaller opening in the
middle of the ring. Finally we set up a policy of documenting which
hand, and which finger we measured on the customer. I can’t count
how many times we measured their left hand but they tried the ring
on their right.

Arthur Anton Skuratowicz GJG (GIA)