How To Accurately Measure Your Ring Size

Measuring Your Ring Size

Determining your ring size is one of the most important parts of ordering a custom ring. Most custom rings cannot be resized, especially those with an inlay. Ordering the wrong size is inconvenient for everyone involved, so it's best to get it right the first time! Follow the steps below to ensure that you get the correct size, before you order your final ring.

How should your ring fit?

A ring that fits is a ring you forget that you're wearing. Here are some useful guidelines for determining a proper fitting ring.

Your fingers change in size very slightly over time, which means that there is no "perfect" ring size. For many, a good fit means comfortable most of the time. There are days when rings are too tight, and days when they’re a little loose. Your fingers fluctuate in size during the day due to temperature, diet, activities, and other factors. Even the time of the year can contribute to a ring not fitting comfortably. You may notice it feeling tighter in warmer months and looser in winter months. In the winter, try and keep your hands warm while sizing to ensure it will fit in the summer. If your hands stay cold while sizing, then your ring might be tighter in the summer.

So how do you know when you have a good fit? A good rule of thumb is that when a ring fits easily over your knuckle, you should be able to get it on without struggle and then have a slight pull at the knuckle when removing it. You may need to twist the ring 1-2 times to get it off. Proper sizing is more of a personal preference than a perfect science.

Finger shape also plays a large role in determining the right fit of a ring. Some fingers are largest at the base and gradually taper without a prominent knuckle. On this type of finger, the ring should fit snugly at the base of the finger without causing bulges or a permanent indent. You should be able to push the ring up from the underside of your finger, and see a small space between the ring and the top of the finger, this gives your finger some breathing room.

Sizing fingers that are largest at the knuckle can be a bit trickier. The key here is to size the ring so it fits comfortably over the knuckle without being too large for the base of the finger. If there is a large size difference between the knuckle and base of the finger, the ring tends to spin and turn on the hand– especially in engagement rings which tend to be top heavy. A simple fix for this is to add sizing beads to the inside of the ring. They prevent some of the spinning while still maintaining a comfortable fit over the knuckle. See how much goes into making a ring fit and sit right? All this information may seem intimidating but what it comes down to is that comfort is key.

As stated before, rings with inlays cannot be resized. This is because the inlays go all around the ring with no joints. The inlays are handmade and cut out of solid pieces (Ex. Wood, Dinosaur Bone, Meteorite, Deer Antler) before they are inlaid on a metal (Ex. Titanium, Sterling Silver, Stainless Steel, Gold). All the more reason to make sure you get the correct ring size, the first time around.

Step 1: Visit at least two reputable jewelers.

You may need to visit more than two, but the goal is to find two jewelers who both agree on your size. Ask them to use a “caliper” or “micrometer” to measure. Probably the most accurate measurement to provide to your custom jeweler is the inside diameter of the ring in millimeters. If you have an existing ring in the same width and fit you are planning to buy, ask the jewelers to measure the inside diameter of this ring. That way you will know exactly what size to order your new ring in.

Keep in mind: All rings here at Jewelry by Johan have a Custom Comfort Fit (there are rare exceptions and those will be noted on the product listing). If you plan to order a ring from us, be sure to ask your local jewelers to measure your size in a Comfort Fit.


Step 2: Determine The Ring Width You Want.

Something to consider when getting your ring size taken is the width of the ring you want to order. Get sized in the particular width you are ordering because wider rings fit more snug than dainty rings. The wider the ring, the tighter you’ll feel it on your finger – so that’s why the size should go up alongside the width in some cases. Most plastic ring sizers have a total width of 3.5mm. If you purchase a ring with a total width of 8mm, your ring size will probably increase by a quarter size from the ring sizer that fit you best.

Step 3: Consider Comfort Fit vs. Standard Ring Sizes

All of our rings are made with a Comfort Fit unless you request otherwise. Comfort Fit rings are made with a slight curve on the interior sleeve of the ring, as opposed to a flat interior on the inside of a Standard Fit ring (illustrated in the picture below). Comfort Fit rings tend to go over the knuckle more easily and fit at the base of your finger better. Overall, they are simply more comfortable, especially for someone that is not used to wearing a ring every day. The interior curve of Comfort Fit rings is not noticeable to anyone looking at the ring on your hand, so if you’re worried that this type of fit will change the look of your ring, have no fear! It’s only on the inside – and it’s very subtle.

Because of the slight rounded interior, a comfort fit band will fit slightly larger than the same size in a standard fit. This is because the size is taken from the peak of the rounded interior (the size read from the middle of the band on a mandrel) and not from one side to the other (read on the mandrel from the bottom of the ring). This is how confusion arises when getting your ring size measured at many jewelers. Ensure the jeweler knows that you want a ring with a comfort fit.

How to Measure a Ring with a Mandrel

Mandrel Measurement

When measuring a ring using a ring size mandrel, one must take note of the interior profile of the ring in order to ensure proper sizing. Though all ring sizes are read the same, where to read the interior profile of a ring can be confusing. When a ring size is taken, the measurement is read where the edge makes contact with the ring size mandrel, i.e its inside diameter. The image above shows a ring that is US size 8.25.

Note: There are a lot of different ring size mandrel manufacturing companies worldwide and their sizes vary depending which one is used. Approximately 50% of them will be off at least ⅛ size and up to ¾ of a size and must be returned.


How to Measure a Ring With Calipers

A ring’s size can be determined by using a caliper, but it requires some math and can be easier on plain bands. The following example illustrates how properly measuring both a comfort fit and standard fit ring will result in the same, accurate size.

1.Measure the outside diameter (OD) of the ring in three different spots and record.

Record the average of these three measurements. In this case, the outer diameter averages out at 23.92 mm.

2.Measure the thickness of the ring in three different places and record the results.

The process is the same for both comfort fit (rounded) and standard fit (flat) ring sleeves. However, the measurements are affected by the sleeve profile:

Again, record the average of these three measurements. In our examples, the comfort fit ring was an average of 2.82 mm thick, and the standard fit was an average of 2.77 mm thick.

3. Take the average outside diameter and subtract the average thickness twice; this will result in the inside diameter of the ring.

Comfort: 23.92-2.82-2.82= 18.28 mm inside diameter

Standard: 23.92-2.77-2.77=18.38 mm inside diameter

After referring to the conversion chart below, we learn that a ring with an inner diameter of between 18.28 mm and 18.38 mm is equal U.S. size 8.25!


Step 4: Order Our Custom Ring Sizers

A few jewelers (like us!) offer the option to purchase custom ring sizers. These plastic sizers are made in the exact width & fit of the ring that you’re ordering and are only $10 each. Using this method allows you to actually feel and see how the ring will look on you before ordering the real thing.

See below for our International Ring Sizing Chart. This will help you determine your size if ordering from another country.

International Ring Sizes

The size of a ring is measured using several different systems. If you know your your ring size in a scale other than the US system, you can use the chart below to convert your measurement to the sizing terms used by Jewelry by Johan.

International Ring Size Conversion Chart
US Size Diameter (mm) Circumference (mm) British French German Japanese Swiss
2.000 13.19 41.43 D   13.50 2 1.75
2.125 13.29 41.76          
2.250 13.39 42.08 D 1/2 42     2.25
2.375 13.50 42.41          
2.500 13.60 42.73 E   13.75 3 3.00
2.625 13.71 43.06   43      
2.750 13.81 43.38 E 1/2       3.5
2.875 13.91 43.71          
3.000 14.02 44.03 F 44 14 4 4.25
3.125 14.12 44.36          
3.250 14.22 44.68 F 1/2     5 4.75
3.375 14.33 45.01   45      
3.500 14.43 45.34 G   14.50   5.5
3.625 14.53 45.66          
3.750 14.64 45.99 G 1/2 46   6 6.00
3.875 14.74 46.31          
4.000 14.85 46.64 H   15 7 6.75
4.125 14.95 46.96   47      
4.250 15.05 47.29 H 1/2       7.50
4.375 15.16 47.61          
4.500 15.26 47.94 I 48 15.25 8 8
4.625 15.36 48.26     15.50    
4.750 15.47 48.59 J       8.75
4.875 15.57 48.92   49      
5.000 15.67 49.24 J 1/2   15.75 9 9.25
5.125 15.78 49.57          
5.250 15.88 49.89 K 50     10
5.375 15.98 50.22          
5.500 16.09 50.54 K 1/2   16 10  
5.625 16.19 50.87   51      
5.750 16.30 51.19 L       11.25
5.875 16.40 51.52          
6.000 16.50 51.85 L 1/2 52 16.50 11 11.75
6.125 16.61 52.17          
6.250 16.71 52.50 M     12 12.5
6.375 16.81 52.82   53      
6.500 16.92 53.15 M 1/2   17 13 13.25
6.625 17.02 53.47          
6.750 17.12 53.80 N 54     13.75
6.875 17.23 54.12          
7.000 17.33 54.45 N 1/2   17.25 14 14.50
7.125 17.44 54.77   55      
7.250 17.54 55.10 O       15
7.375 17.64 55.43          
7.500 17.75 55.75 O 1/2 56 17.75 15 15.75
7.625 17.85 56.08          
7.750 17.95 56.40 P       16.25
7.875 18.06 56.73   57      
8.000 18.16 57.05 P 1/2   18 16 17.00
8.125 18.26 57.38          
8.250 18.37 57.70 Q 58     17.5
8.375 18.47 58.03          
8.500 18.57 58.35 Q 1/2   18.50 17 18.25
8.625 18.68 58.68   59      
8.750 18.78 59.01 R       19
8.875 18.89 59.33          
9.000 18.99 59.66 R 1/2   19 18 19.5
9.125 19.09 59.98   60      
9.250 19.20 60.31 S       20.25
9.375 19.30 60.63          
9.500 19.40 60.96 S 1/2 61 19.50 19 20.75
9.625 19.51 61.28          
9.750 19.61 61.61 T       21.50
9.875 19.71 61.93   62      
10.000 19.82 62.26 T 1/2   20 20 22
10.125 19.92 62.59          
10.250 20.03 62.91 U 63   21 22.75
10.375 20.13 63.24          
10.500 20.23 63.56 U 1/2   20.25 22 23.25
10.625 20.34 63.89   64      
10.750 20.44 64.21 V       24
10.875 20.54 64.54          
11.000 20.65 64.86 V 1/2 65 20.75 23 24.75
11.125 20.75 65.19          
11.250 20.85 65.51 W       25.25
11.375 20.96 65.84   66      
11.500 21.06 66.17 W 1/2   21 24 26
11.625 21.16 66.49          
11.750 21.27 66.82 X 67     26.5
11.875 21.37 67.14          
12.000 21.48 67.47 X 1/2   21.25 25 27.25
12.125 21.58 67.79   68      
12.250 21.68 68.12 Y       27.75
12.375 21.79 68.44          
12.500 21.89 68.77 Z 69 21.75 26 28.50
12.625 21.99 69.09          
12.750 22.10 69.42 Z 1/2       29
12.875 22.20 69.75          
13.000 22.30 70.07     22 27 29.75
13.125 22.41 70.40          
13.250 22.51 70.72 Z1       30.5
13.375 22.62 71.05          
13.500 22.72 71.37         31
13.625 22.82 71.70          
13.750 22.93 72.02 Z2       31.75
13.875 23.03 72.35          
14.000 23.13 72.68 Z3       32.25
14.125 23.24 73.00          
14.250 23.34 73.33         33
14.375 23.44 73.65          
14.500 23.55 73.98 Z4       33.5
14.625 23.65 74.30          
14.750 23.75 74.63         34.25
14.875 23.86 74.95          
15.000 23.96 75.28         34.75
15.125 24.07 75.60          
15.250 24.17 75.93         35.5
15.375 24.27 76.26          
15.500 24.38 76.58         36.25
15.625 24.48 76.91          
15.750 24.58 77.23         36.75
15.875 24.69 77.56          
16.000 24.79 77.88         37.5
16.125 24.89 78.21          
16.250 25.00 78.53          
16.375 25.10 78.86          
16.500 25.21 79.18          
16.625 25.31 79.51          
16.750 25.41 79.84          
16.875 25.52 80.16          
17.000 25.62 80.49          
17.125 25.72 80.81          
17.250 25.83 81.14          
17.375 25.93 81.46          
17.500 26.03 81.79          
17.625 26.14 82.11          
17.750 26.24 82.44          
17.875 26.34 82.76          
18.000 26.45 83.09          
18.125 26.55 83.42          
18.250 26.66 83.74          
18.375 26.76 84.07          
18.500 26.86 84.39          
18.625 26.97 84.72          
18.750 27.07 85.04          
18.875 27.17 85.37          
19.000 27.28 85.69          
19.125 27.38 86.02          
19.250 27.48 86.34          
19.375 27.59 86.67          
19.500 27.69 87.00          
19.625 27.80 87.32          
19.750 27.90 87.65          
19.875 28.00 87.97          
20.000 28.11 88.30          

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