A guide from the maker · Diamond Exchange, Ramat Gan
Ring Size Guide: Measure at Home in a Minute
A ring size is a measurement, not a guess, and you can take it at home with a ring that already fits and a coin from your pocket. Below is a sizer that works on this screen, the full chart in every standard, the ways to find her size without her knowing, and the promise that makes the whole question smaller: if the fit is not perfect, the first resizing is free.
By The DAZZ workshop team·Three generations of diamantaires at the Israel Diamond Exchange·
In this guide
Chapter 01
Measure with a ring you already have
Every phone and laptop screen shows a different physical size for the same picture, so a circle on a screen means nothing until the screen knows its own scale. The sizer below learns it from a coin: match the circle to a coin whose size is known to a hundredth of a millimeter, once, and from then on the circle is true. Then match a ring that fits to the same circle. The reading is the inside diameter in millimeters, converted to every size system.
Step 1 · A coin sets the scale
Put a coin on the circle below and move the slider until the circle matches the coin exactly. Then press Looks right. You only do it once per device.
Why a coin? Every phone and laptop draws the same circle at a different real size, so a circle on a screen means nothing by itself. A coin is made to a hundredth of a millimeter. Once the circle matches the coin, the screen knows its true scale, and the ring you measure next is measured in real millimeters.
Step 2 · Now the ring
Lay a ring that fits the right finger on the screen so that its stone hangs over the right edge of the phone and the band lies flat on the glass. A band that is tilted by a stone or a setting reads a size or two wrong; flat, it reads true. A plain band, or a band set with small stones, lies flat anywhere on the circle. Then adjust until the circle just touches the band’s inside edge all the way round.
Works best with a plain band. If the setting is too deep for the band to lie flat even with the stone off the edge, use the paper strip below instead.
No plain band? Measure the finger
Wrap a strip of paper about 5 mm wide around the base of the finger, snug but not tight, mark where it overlaps, and measure the mark in millimeters with a ruler. Type that number here.
Inside diameter
16.5 mm
US
6
UK
L½
EU
52
Japan
12
Accurate to about half a millimeter with the coin step done with care and the band lying flat. Not sure? Send us a photo of the hand with any ring; and the first resizing is free, at any time.
Chapter 02
Ring size chart: mm, US, UK, EU and Japan
A ring size is just the inside of the ring, written three ways. The US and Canada count in sizes that step by 0.81 mm of diameter; the UK and Australia use letters at the same steps; continental Europe and the ISO standard use the inside circumference in millimeters, which is why an EU 52 is a ring 52 mm around. Japan has its own count. We make rings in every standard, in half sizes and finer on request; tell us whichever you know.
| Inside diameter mm | US | UK | EU / ISO | Japan |
|---|---|---|---|---|
| 14.07 | 3 | F | 44 | 4 |
| 14.47 | 3½ | G | 45 | 5 |
| 14.88 | 4 | H | 47 | 7 |
| 15.29 | 4½ | I | 48 | 8 |
| 15.69 | 5 | J½ | 49 | 9 |
| 16.10 | 5½ | K½ | 51 | 10 |
| 16.51 | 6 | L½ | 52 | 12 |
| 16.91 | 6½ | M½ | 53 | 13 |
| 17.32 | 7 | N½ | 54 | 14 |
| 17.73 | 7½ | O½ | 56 | 15 |
| 18.13 | 8 | P½ | 57 | 16 |
| 18.54 | 8½ | Q½ | 58 | 18 |
| 18.95 | 9 | R½ | 60 | 19 |
| 19.35 | 9½ | S½ | 61 | 20 |
| 19.76 | 10 | T½ | 62 | 21 |
| 20.16 | 10½ | U½ | 63 | 23 |
| 20.57 | 11 | V½ | 65 | 24 |
| 20.98 | 11½ | W½ | 66 | 25 |
| 21.38 | 12 | X½ | 67 | 26 |
| 21.79 | 12½ | Y½ | 68 | 27 |
| 22.20 | 13 | Z½ | 70 | 29 |
Diameters are the US standard (0.8128 mm per size from 11.63 mm). UK letters and Japanese sizes follow the charts most jewelers use; makers round differently by up to a quarter size, which is why we ask for the millimeters when you have them. The shaded rows are the sizes we make most.
Chapter 03
Three ways to measure at home
In order of accuracy. Whichever you use, measure twice, in the evening, and send us both readings if they differ.
A ring that fits, on the sizer above
The most accurate home method, to about half a millimeter, with one condition: the band must lie flat on the glass. A plain band does; a ring with a stone does only if the stone hangs over the edge of the phone, which is how the sizer asks you to place it. Use a ring worn on the same finger of the same hand (the two hands differ by up to half a size), similar in width to the ring you are ordering, and set the scale with a coin first.
A strip of paper around the finger
The method to use when you have no plain band. Cut a strip of paper about 5 mm wide, wrap it around the base of the finger, snug but not tight, and mark where it overlaps. Measure the length in millimeters: that is the circumference, which is the EU size directly; type it into the sizer above or read it off the chart. Then check that the strip, held at that length, passes over the knuckle; if it does not, go up to the knuckle's size. Paper stretches less than string, which is why we prefer it.
A ring that fits, and a ruler
Measure the inside of the ring from edge to edge at its widest, in millimeters, as precisely as you can; a ruler reads to about half a millimeter, which is one size. Find the diameter in the chart. If the ring is not a perfect circle (many are worn slightly oval), measure the longer and shorter inside diameters and average them.
What we would not rely on. A ring measured with its stone resting on the glass: the setting tilts the band and the reading is a size or two out, which is why the sizer asks for the stone over the edge. Printable paper sizers, unless you have checked the printed scale against a ruler; most printers scale the page. String, which stretches. And a ring tried on a different finger, which can be a full size out.
Chapter 04
Finding her size without spoiling the surprise
The one small challenge of a surprise proposal, and the one that most people overthink. In order of how often they work:
A ring she already wears
Borrow, for ten minutes, a ring she wears on the ring finger of the left hand, and measure it on the sizer above or with a ruler. A ring from another finger still helps: tell us which finger, and we will adjust from experience. Put it back exactly where it was.
Press it into something soft
If you cannot bring the ring to a screen, press it into a bar of soap or a piece of clay and measure the inside of the impression later. Old-fashioned, and surprisingly accurate.
Ask someone close
Her mother, a sister or a close friend often knows, or would happily find out on a shopping afternoon. Jewelers measure for free; a friend who "tries rings on with her" learns the size in minutes.
A photo of her hand
A photo of her hand wearing any ring, sent to us with a word about which finger, is enough for a good estimate; see chapter 06. We have done this thousands of times.
The safety net
Whatever you choose, do not let the size hold you back. If the fit is not perfect after the proposal, we resize the ring; the first resizing is free at any time, and only the shipping to our workshop and back is at your expense. Most surprise proposals end with a resize of half a size, and that is normal.
Chapter 05
What changes a ring size
The time of day, and the weather
Fingers are smallest in the morning and in the cold, and largest in the evening, in heat and after exercise or salty food, by up to half a size. Measure in the evening, at room temperature, and if two readings disagree, take the larger.
The knuckle
A ring must pass the knuckle to reach the base of the finger. On a hand with a prominent knuckle the right size is between the knuckle and the base: slightly loose at the base, so that it passes over the joint. If the gap is large, tell us; we can set small sizing beads inside the band.
The width of the band
A wide band sits on more of the finger and feels tighter than a slim one of the same size. For a band 6 mm or wider, go up by about half a size from a measurement taken with a slim ring. Our solitaires and pavé bands are slim; our wider bands say so on the page.
Pregnancy, weight and age
Fingers change. A size taken years ago, or during a pregnancy, is a starting point rather than an answer; measure again now. Over a lifetime most people go up a size or two, which is one reason the first resizing is free and later ones are a modest fee.
The two hands
The dominant hand is usually a quarter to half a size larger. Measure the hand the ring will be worn on; for an engagement ring in most countries that is the left.
Chapter 06
Not sure? Send us a photo
After thousands of rings and thousands of hands, a photo tells us a great deal. Send us a picture of the hand wearing any ring, a word about which finger it is worn on, and the ring’s size if you happen to know it, and we will give you our estimate, usually the same working day. It is not a laboratory measurement; it is experience, and for a surprise it is nearly always enough.
And the promise underneath it all. The first resizing of any ring we make is free, at any time, no questions asked; only the shipping to our workshop at the Exchange and back is at your expense. We say it on every product page because it changes the question from “what if I get it wrong?” to “what size do you think?”, and the second question has an answer.
first resizing free · reply within one business day · made to order in about 10 business days
Chapter 07
How to tell us the size
In any standard you like. The order request on every product page has a size field in US sizes and an “I am not sure yet” option, which is a perfectly good answer: we will ask the two or three questions we need and settle it together before the ring is made. If you measured in millimeters, write the millimeters; it is the most precise thing you can send us, and we size to the millimeter.
In the ring builder the size is asked for at the end, with the same option. And if you are ordering a surprise, say so: we pack the ring so that a resize later is simple, and we keep the measurements on file.
Chapter 08
What we see in our workshop
We size rings every day, so here is the question from our side of the bench, with the caveat that this is our experience and not a survey.
Most sizes are right, or half a size out. Of the rings we make for customers abroad, the great majority fit as ordered, and nearly all the rest need half a size either way. A full size out is rare, and it almost always comes from a ring measured on the wrong finger or the wrong hand.
Surprises resize more, and that is fine. A ring ordered in secret comes back for a half-size adjustment more often than one ordered together, which is exactly what the free first resizing is for. Nobody has ever minded; the proposal has already happened.
The photo works. We have been estimating sizes from photographs of hands for years, long before this page existed, and our estimates land within half a size most of the time. Send the photo; it costs nothing and it usually settles it.
Questions and answers
What we are asked about ring sizes
The most accurate way is a ring that already fits: lay it on the sizer at the top of this page, after setting the scale with a coin, and match the circle to its inside edge. Without a ring, wrap a 5 mm strip of paper around the base of the finger, mark the overlap and measure it in millimeters; that is the EU size, and the chart converts it.
We would love to meet you
The door is open
Message us on WhatsApp, book a video appointment, or, when you are in Israel, visit us at the Israel Diamond Exchange in Ramat Gan.